diff --git a/src/pretix/api/serializers/event.py b/src/pretix/api/serializers/event.py
index 0809cfe24c..34afa9ef5d 100644
--- a/src/pretix/api/serializers/event.py
+++ b/src/pretix/api/serializers/event.py
@@ -623,6 +623,9 @@ class EventSettingsSerializer(serializers.Serializer):
         'cancel_allow_user_paid_adjust_fees_explanation',
         'cancel_allow_user_paid_refund_as_giftcard',
         'cancel_allow_user_paid_require_approval',
+        'change_allow_user_variation',
+        'change_allow_user_until',
+        'change_allow_user_price',
     ]
 
     def __init__(self, *args, **kwargs):
diff --git a/src/pretix/base/email.py b/src/pretix/base/email.py
index 9f3dd0605d..46578d97c1 100644
--- a/src/pretix/base/email.py
+++ b/src/pretix/base/email.py
@@ -315,6 +315,51 @@ def base_placeholders(sender, **kwargs):
                 }
             ),
         ),
+        SimpleFunctionalMailTextPlaceholder(
+            'url_info_change', ['order', 'event'], lambda order, event: build_absolute_uri(
+                event,
+                'presale:event.order.modify', kwargs={
+                    'order': order.code,
+                    'secret': order.secret,
+                }
+            ), lambda event: build_absolute_uri(
+                event,
+                'presale:event.order.modify', kwargs={
+                    'order': 'F8VVL',
+                    'secret': '6zzjnumtsx136ddy',
+                }
+            ),
+        ),
+        SimpleFunctionalMailTextPlaceholder(
+            'url_products_change', ['order', 'event'], lambda order, event: build_absolute_uri(
+                event,
+                'presale:event.order.change', kwargs={
+                    'order': order.code,
+                    'secret': order.secret,
+                }
+            ), lambda event: build_absolute_uri(
+                event,
+                'presale:event.order.change', kwargs={
+                    'order': 'F8VVL',
+                    'secret': '6zzjnumtsx136ddy',
+                }
+            ),
+        ),
+        SimpleFunctionalMailTextPlaceholder(
+            'url_cancel', ['order', 'event'], lambda order, event: build_absolute_uri(
+                event,
+                'presale:event.order.cancel', kwargs={
+                    'order': order.code,
+                    'secret': order.secret,
+                }
+            ), lambda event: build_absolute_uri(
+                event,
+                'presale:event.order.cancel', kwargs={
+                    'order': 'F8VVL',
+                    'secret': '6zzjnumtsx136ddy',
+                }
+            ),
+        ),
         SimpleFunctionalMailTextPlaceholder(
             'url', ['event', 'position'], lambda event, position: build_absolute_uri(
                 event,
diff --git a/src/pretix/base/models/items.py b/src/pretix/base/models/items.py
index bbb67525a5..603dc652d7 100644
--- a/src/pretix/base/models/items.py
+++ b/src/pretix/base/models/items.py
@@ -378,9 +378,9 @@ class Item(LoggedModel):
                     'but only for fixed bundles!')
     )
     allow_cancel = models.BooleanField(
-        verbose_name=_('Allow product to be canceled'),
+        verbose_name=_('Allow product to be canceled or changed'),
         default=True,
-        help_text=_('If this is checked, the usual cancellation settings of this event apply. If this is unchecked, '
+        help_text=_('If this is checked, the usual cancellation and order change settings of this event apply. If this is unchecked, '
                     'orders containing this product can not be canceled by users but only by you.')
     )
     min_per_order = models.IntegerField(
diff --git a/src/pretix/base/models/orders.py b/src/pretix/base/models/orders.py
index b0faf10435..4b62a0c9dc 100644
--- a/src/pretix/base/models/orders.py
+++ b/src/pretix/base/models/orders.py
@@ -434,6 +434,19 @@ class Order(LockModel, LoggedModel):
             self.status in (Order.STATUS_PENDING, Order.STATUS_PAID, Order.STATUS_EXPIRED) and self.count_positions
         )
 
+    @cached_property
+    def user_change_deadline(self):
+        until = self.event.settings.get('change_allow_user_until', as_type=RelativeDateWrapper)
+        if until:
+            if self.event.has_subevents:
+                terms = [
+                    until.datetime(se)
+                    for se in self.event.subevents.filter(id__in=self.positions.values_list('subevent', flat=True))
+                ]
+                return min(terms) if terms else None
+            else:
+                return until.datetime(self.event)
+
     @cached_property
     def user_cancel_deadline(self):
         if self.status == Order.STATUS_PAID and self.total != Decimal('0.00'):
@@ -466,6 +479,36 @@ class Order(LockModel, LoggedModel):
             fee += self.event.settings.cancel_allow_user_paid_keep
         return round_decimal(fee, self.event.currency)
 
+    @property
+    @scopes_disabled()
+    def user_change_allowed(self) -> bool:
+        """
+        Returns whether or not this order can be canceled by the user.
+        """
+        from .checkin import Checkin
+
+        if self.status not in (Order.STATUS_PENDING, Order.STATUS_PAID) or not self.count_positions:
+            return False
+
+        if self.cancellation_requests.exists():
+            return False
+        positions = list(
+            self.positions.all().annotate(
+                has_variations=Exists(ItemVariation.objects.filter(item_id=OuterRef('item_id'))),
+                has_checkin=Exists(Checkin.objects.filter(position_id=OuterRef('pk')))
+            ).select_related('item').prefetch_related('issued_gift_cards')
+        )
+        cancelable = all([op.item.allow_cancel and not op.has_checkin for op in positions])
+        if not cancelable or not positions:
+            return False
+        for op in positions:
+            if op.issued_gift_cards.all():
+                return False
+        if self.user_change_deadline and now() > self.user_change_deadline:
+            return False
+
+        return self.event.settings.change_allow_user_variation and any([op.has_variations for op in positions])
+
     @property
     @scopes_disabled()
     def user_cancel_allowed(self) -> bool:
@@ -474,7 +517,7 @@ class Order(LockModel, LoggedModel):
         """
         from .checkin import Checkin
 
-        if self.cancellation_requests.exists():
+        if self.cancellation_requests.exists() or not self.cancel_allowed():
             return False
         positions = list(
             self.positions.all().annotate(
diff --git a/src/pretix/base/services/orders.py b/src/pretix/base/services/orders.py
index ecdd0cd4f1..a895dd0a88 100644
--- a/src/pretix/base/services/orders.py
+++ b/src/pretix/base/services/orders.py
@@ -1131,7 +1131,7 @@ def notify_user_changed_order(order, user=None, auth=None, invoices=[]):
         try:
             order.send_mail(
                 email_subject, email_template, email_context,
-                'pretix.event.order.email.order_changed', user, auth=auth, invoices=invoices,
+                'pretix.event.order.email.order_changed', user, auth=auth, invoices=invoices, attach_tickets=True,
             )
         except SendMailException:
             logger.exception('Order changed email could not be sent')
@@ -1869,9 +1869,10 @@ class OrderChangeManager:
 
     def _reissue_invoice(self):
         i = self.order.invoices.filter(is_cancellation=False).last()
-        if self.reissue_invoice and i and self._invoice_dirty:
-            self._invoices.append(generate_cancellation(i))
-            if invoice_qualified(self.order):
+        if self.reissue_invoice and self._invoice_dirty:
+            if i:
+                self._invoices.append(generate_cancellation(i))
+            if (i or self.event.settings.invoice_generate == 'True') and invoice_qualified(self.order):
                 self._invoices.append(generate_invoice(self.order))
 
     def _check_complete_cancel(self):
diff --git a/src/pretix/base/services/quotas.py b/src/pretix/base/services/quotas.py
index 22f99c5eed..7d6a97ef00 100644
--- a/src/pretix/base/services/quotas.py
+++ b/src/pretix/base/services/quotas.py
@@ -89,7 +89,7 @@ class QuotaAvailability:
 
     def compute(self, now_dt=None):
         now_dt = now_dt or now()
-        quotas = list(self._queue)
+        quotas = list(set(self._queue))
         quotas_original = list(self._queue)
         self._queue.clear()
         if not quotas:
diff --git a/src/pretix/base/settings.py b/src/pretix/base/settings.py
index fe535662bf..e176198a06 100644
--- a/src/pretix/base/settings.py
+++ b/src/pretix/base/settings.py
@@ -925,6 +925,46 @@ DEFAULTS = {
                         "multiple event dates, the earliest date will be used."),
         )
     },
+    'change_allow_user_variation': {
+        'default': 'False',
+        'type': bool,
+        'form_class': forms.BooleanField,
+        'serializer_class': serializers.BooleanField,
+        'form_kwargs': dict(
+            label=_("Customers can change the variation of the products they purchased"),
+        )
+    },
+    'change_allow_user_price': {
+        'default': 'gt',
+        'type': str,
+        'form_class': forms.ChoiceField,
+        'serializer_class': serializers.ChoiceField,
+        'serializer_kwargs': dict(
+            choices=(
+                ('gt', _('Only allow changes if the resulting price is higher or equal than the previous price.')),
+                ('eq', _('Only allow changes if the resulting price is equal to the previous price.')),
+                ('any', _('Allow changes regardless of price, even if this results in a refund.')),
+            )
+        ),
+        'form_kwargs': dict(
+            label=_("Requirement for changed prices"),
+            choices=(
+                ('gt', _('Only allow changes if the resulting price is higher or equal than the previous price.')),
+                ('eq', _('Only allow changes if the resulting price is equal to the previous price.')),
+                ('any', _('Allow changes regardless of price, even if this results in a refund.')),
+            ),
+            widget=forms.RadioSelect,
+        ),
+    },
+    'change_allow_user_until': {
+        'default': None,
+        'type': RelativeDateWrapper,
+        'form_class': RelativeDateTimeField,
+        'serializer_class': SerializerRelativeDateTimeField,
+        'form_kwargs': dict(
+            label=_("Do not allow changes after"),
+        )
+    },
     'cancel_allow_user': {
         'default': 'True',
         'type': bool,
diff --git a/src/pretix/base/templatetags/money.py b/src/pretix/base/templatetags/money.py
index 75e5adac33..a06d3a1634 100644
--- a/src/pretix/base/templatetags/money.py
+++ b/src/pretix/base/templatetags/money.py
@@ -37,7 +37,7 @@ def money_filter(value: Decimal, arg='', hide_currency=False):
                 arg,
                 floatformat(value, 2)
             )
-        return format_currency(value, arg, locale=translation.get_language())
+        return format_currency(value, arg, locale=translation.get_language()[:2])
     except:
         return '{} {}'.format(
             arg,
diff --git a/src/pretix/control/forms/event.py b/src/pretix/control/forms/event.py
index 9c1c12f923..d0e6750852 100644
--- a/src/pretix/control/forms/event.py
+++ b/src/pretix/control/forms/event.py
@@ -575,6 +575,9 @@ class CancelSettingsForm(SettingsForm):
         'cancel_allow_user_paid_adjust_fees_explanation',
         'cancel_allow_user_paid_refund_as_giftcard',
         'cancel_allow_user_paid_require_approval',
+        'change_allow_user_variation',
+        'change_allow_user_price',
+        'change_allow_user_until',
     ]
 
     def __init__(self, *args, **kwargs):
diff --git a/src/pretix/control/templates/pretixcontrol/event/cancel.html b/src/pretix/control/templates/pretixcontrol/event/cancel.html
index d2cdd9ae14..5ef9f4bc7d 100644
--- a/src/pretix/control/templates/pretixcontrol/event/cancel.html
+++ b/src/pretix/control/templates/pretixcontrol/event/cancel.html
@@ -38,6 +38,17 @@
                     </div>
                 {% endif %}
             </fieldset>
+            <fieldset>
+                <legend>{% trans "Order changes" %}</legend>
+                <div class="alert alert-info">
+                    {% blocktrans trimmed %}
+                        Allowing users to change their order is a feature under development. Therefore, currently only specific changes (such as changing the variation of a product) are possible. More options might be added later.
+                    {% endblocktrans %}
+                </div>
+                {% bootstrap_field form.change_allow_user_variation layout="control" %}
+                {% bootstrap_field form.change_allow_user_price layout="control" %}
+                {% bootstrap_field form.change_allow_user_until layout="control" %}
+            </fieldset>
         </div>
         <div class="form-group submit-group">
             <button type="submit" class="btn btn-primary btn-save">
diff --git a/src/pretix/presale/forms/order.py b/src/pretix/presale/forms/order.py
new file mode 100644
index 0000000000..b68a8c0eb1
--- /dev/null
+++ b/src/pretix/presale/forms/order.py
@@ -0,0 +1,96 @@
+from decimal import Decimal
+
+from django import forms
+from django.utils.translation import ugettext_lazy as _
+
+from pretix.base.models import Quota
+from pretix.base.models.tax import TaxedPrice
+from pretix.base.services.pricing import get_price
+from pretix.base.services.quotas import QuotaAvailability
+from pretix.base.templatetags.money import money_filter
+
+
+class OrderPositionChangeForm(forms.Form):
+    itemvar = forms.ChoiceField(
+        label=_('Product'),
+        required=False,
+    )
+
+    def __init__(self, *args, **kwargs):
+        instance = kwargs.pop('instance')
+        invoice_address = kwargs.pop('invoice_address')
+        initial = kwargs.get('initial', {})
+        event = kwargs.pop('event')
+        kwargs['initial'] = initial
+        if instance.variation_id:
+            initial['itemvar'] = f'{instance.item_id}-{instance.variation_id}'
+        else:
+            initial['itemvar'] = f'{instance.item_id}'
+
+        super().__init__(*args, **kwargs)
+
+        choices = []
+
+        i = instance.item
+        pname = str(i)
+        variations = list(i.variations.all())
+
+        if variations:
+            current_quotas = instance.variation.quotas.all() if instance.variation else instance.item.quotas.all()
+            qa = QuotaAvailability()
+            for v in variations:
+                qa.queue(*v.quotas.all())
+            qa.compute()
+
+            for v in variations:
+
+                label = f'{i.name} – {v.value}'
+                if instance.variation_id == v.id:
+                    choices.append((f'{i.pk}-{v.pk}', label))
+                    continue
+
+                if not v.active:
+                    continue
+
+                q_res = [qa.results[q][0] != Quota.AVAILABILITY_OK for q in v.quotas.all() if q not in current_quotas]
+                if not v.quotas.all() or (q_res and any(q_res)):
+                    continue
+
+                new_price = get_price(i, v, voucher=instance.voucher, subevent=instance.subevent,
+                                      invoice_address=invoice_address)
+                current_price = TaxedPrice(tax=instance.tax_value, gross=instance.price, net=instance.price - instance.tax_value,
+                                           name=instance.tax_rule.name if instance.tax_rule else '', rate=instance.tax_rate)
+                if new_price.gross < current_price.gross and event.settings.change_allow_user_price == 'gt':
+                    continue
+                if new_price.gross != current_price.gross and event.settings.change_allow_user_price == 'eq':
+                    continue
+
+                if new_price.gross < current_price.gross:
+                    if event.settings.display_net_prices:
+                        label += ' (- {} {})'.format(money_filter(current_price.gross - new_price.gross, event.currency), _('plus taxes'))
+                    else:
+                        label += ' (- {})'.format(money_filter(current_price.gross - new_price.gross, event.currency))
+                elif current_price.gross < new_price.gross:
+                    if event.settings.display_net_prices:
+                        label += ' ({}{} {})'.format(
+                            '+ ' if current_price.gross != Decimal('0.00') else '',
+                            money_filter(new_price.gross - current_price.gross, event.currency),
+                            _('plus taxes')
+                        )
+                    else:
+                        label += ' ({}{})'.format(
+                            '+ ' if current_price.gross != Decimal('0.00') else '',
+                            money_filter(new_price.gross - current_price.gross, event.currency)
+                        )
+
+                choices.append((f'{i.pk}-{v.pk}', label))
+
+            if not choices:
+                self.fields['itemvar'].widget.attrs['disabled'] = True
+                self.fields['itemvar'].help_text = _('No other variation of this product is currently available for you.')
+        else:
+            choices.append((str(i.pk), '%s' % pname))
+            self.fields['itemvar'].widget.attrs['disabled'] = True
+            self.fields['itemvar'].help_text = _('No other variations of this product exist.')
+
+        self.fields['itemvar'].choices = choices
diff --git a/src/pretix/presale/templates/pretixpresale/event/order.html b/src/pretix/presale/templates/pretixpresale/event/order.html
index 32305c9760..bbe26b94ba 100644
--- a/src/pretix/presale/templates/pretixpresale/event/order.html
+++ b/src/pretix/presale/templates/pretixpresale/event/order.html
@@ -312,92 +312,110 @@
         {% endif %}
         <div class="clearfix"></div>
     </div>
-    {% if order.cancel_allowed and order.user_cancel_allowed %}
+    {% if order.user_change_allowed or order.user_cancel_allowed %}
         <div class="panel panel-primary panel-cancellation">
             <div class="panel-heading">
                 <h3 class="panel-title">
-                    {% trans "Cancellation" context "action" %}
+                    {% trans "Change or cancel your order" context "action" %}
                 </h3>
             </div>
-            <div class="panel-body">
-                {% if order.status == "p" and order.total != 0 %}
-                    {% if order.user_cancel_fee >= order.total %}
+            <ul class="list-group">
+                {% if order.user_change_allowed %}
+                    <li class="list-group-item">
                         <p>
-                            {% if request.event.settings.cancel_allow_user_paid_require_approval %}
-                                {% blocktrans trimmed %}
-                                    You can request to cancel this order, but you will not receive a refund.
-                                {% endblocktrans %}
-                            {% else %}
-                                {% blocktrans trimmed %}
-                                    You can cancel this order, but you will not receive a refund.
-                                {% endblocktrans %}
-                            {% endif %}
-                            {% trans "This will invalidate all tickets in this order." %}
+                            {% blocktrans trimmed %}
+                                If you want to make changes to the products you bought, you can click on the button to change your order.
+                            {% endblocktrans %}
                         </p>
-                    {% elif order.user_cancel_fee %}
-                        <p>
-                            {% if request.event.settings.cancel_allow_user_paid_require_approval %}
-                                {% blocktrans trimmed with fee=order.user_cancel_fee|money:request.event.currency %}
-                                    You can request to cancel this order. If your request is approved, a cancellation
-                                    fee of <strong>{{ fee }}</strong> will be kept and you will receive a refund of
-                                    the remainder.
-                                {% endblocktrans %}
-                            {% else %}
-                                {% blocktrans trimmed with fee=order.user_cancel_fee|money:request.event.currency %}
-                                    You can cancel this order. In this case, a cancellation fee of <strong>{{ fee }}</strong>
-                                    will be kept and you will receive a refund of the remainder.
-                                {% endblocktrans %}
-                            {% endif %}
-                            {% if request.event.settings.cancel_allow_user_paid_refund_as_giftcard == "force" %}
-                                {% trans "The refund will be issued in form of a gift card that you can use for further purchases." %}
-                            {% elif request.event.settings.cancel_allow_user_paid_refund_as_giftcard == "option" %}
-                                {% trans "The refund can be issued to your original payment method or as a gift card." %}
-                            {% else %}
-                                {% trans "The refund will be issued to your original payment method." %}
-                            {% endif %}
-                            {% trans "This will invalidate all tickets in this order." %}
-                        </p>
-                    {% else %}
-                        <p>
-                            {% if request.event.settings.cancel_allow_user_paid_require_approval %}
-                                {% blocktrans trimmed %}
-                                    You can request to cancel this order. If your request is approved, you get a full
-                                    refund.
-                                {% endblocktrans %}
-                            {% else %}
-                                {% blocktrans trimmed %}
-                                    You can cancel this order and receive a full refund.
-                                {% endblocktrans %}
-                            {% endif %}
-                            {% if request.event.settings.cancel_allow_user_paid_refund_as_giftcard == "force" %}
-                                {% trans "The refund will be issued in form of a gift card that you can use for further purchases." %}
-                            {% elif request.event.settings.cancel_allow_user_paid_refund_as_giftcard == "option" %}
-                                {% trans "The refund can be issued to your original payment method or as a gift card." %}
-                            {% else %}
-                                {% trans "The refund will be issued to your original payment method." %}
-                            {% endif %}
-                            {% trans "This will invalidate all tickets in this order." %}
-                        </p>
-                    {% endif %}
-                    <a href="{% eventurl event 'presale:event.order.cancel' secret=order.secret order=order.code %}"
-                       class="btn btn-danger">
-                        <span class="fa fa-remove"></span>
-                        {% trans "Cancel order" %}
-                    </a>
-                {% else %}
-                    <p>
-                        {% blocktrans trimmed %}
-                            You can cancel this order using the following button.
-                        {% endblocktrans %}
-                        {% trans "This will invalidate all tickets in this order." %}
-                    </p>
-                    <a href="{% eventurl event 'presale:event.order.cancel' secret=order.secret order=order.code %}"
-                        class="btn btn-danger">
-                        <span class="fa fa-remove"></span>
-                        {% trans "Cancel order" %}
-                    </a>
+                        <a href="{% eventurl event 'presale:event.order.change' secret=order.secret order=order.code %}"
+                                class="btn btn-default">
+                            <span class="fa fa-edit"></span>
+                            {% trans "Change order" %}
+                        </a>
+                    </li>
                 {% endif %}
-            </div>
+                {% if order.user_cancel_allowed %}
+                    <li class="list-group-item">
+                        {% if order.status == "p" and order.total != 0 %}
+                            {% if order.user_cancel_fee >= order.total %}
+                                <p>
+                                    {% if request.event.settings.cancel_allow_user_paid_require_approval %}
+                                        {% blocktrans trimmed %}
+                                            You can request to cancel this order, but you will not receive a refund.
+                                        {% endblocktrans %}
+                                    {% else %}
+                                        {% blocktrans trimmed %}
+                                            You can cancel this order, but you will not receive a refund.
+                                        {% endblocktrans %}
+                                    {% endif %}
+                                    {% trans "This will invalidate all tickets in this order." %}
+                                </p>
+                            {% elif order.user_cancel_fee %}
+                                <p>
+                                    {% if request.event.settings.cancel_allow_user_paid_require_approval %}
+                                        {% blocktrans trimmed with fee=order.user_cancel_fee|money:request.event.currency %}
+                                            You can request to cancel this order. If your request is approved, a cancellation
+                                            fee of <strong>{{ fee }}</strong> will be kept and you will receive a refund of
+                                            the remainder.
+                                        {% endblocktrans %}
+                                    {% else %}
+                                        {% blocktrans trimmed with fee=order.user_cancel_fee|money:request.event.currency %}
+                                            You can cancel this order. In this case, a cancellation fee of <strong>{{ fee }}</strong>
+                                            will be kept and you will receive a refund of the remainder.
+                                        {% endblocktrans %}
+                                    {% endif %}
+                                    {% if request.event.settings.cancel_allow_user_paid_refund_as_giftcard == "force" %}
+                                        {% trans "The refund will be issued in form of a gift card that you can use for further purchases." %}
+                                    {% elif request.event.settings.cancel_allow_user_paid_refund_as_giftcard == "option" %}
+                                        {% trans "The refund can be issued to your original payment method or as a gift card." %}
+                                    {% else %}
+                                        {% trans "The refund will be issued to your original payment method." %}
+                                    {% endif %}
+                                    {% trans "This will invalidate all tickets in this order." %}
+                                </p>
+                            {% else %}
+                                <p>
+                                    {% if request.event.settings.cancel_allow_user_paid_require_approval %}
+                                        {% blocktrans trimmed %}
+                                            You can request to cancel this order. If your request is approved, you get a full
+                                            refund.
+                                        {% endblocktrans %}
+                                    {% else %}
+                                        {% blocktrans trimmed %}
+                                            You can cancel this order and receive a full refund.
+                                        {% endblocktrans %}
+                                    {% endif %}
+                                    {% if request.event.settings.cancel_allow_user_paid_refund_as_giftcard == "force" %}
+                                        {% trans "The refund will be issued in form of a gift card that you can use for further purchases." %}
+                                    {% elif request.event.settings.cancel_allow_user_paid_refund_as_giftcard == "option" %}
+                                        {% trans "The refund can be issued to your original payment method or as a gift card." %}
+                                    {% else %}
+                                        {% trans "The refund will be issued to your original payment method." %}
+                                    {% endif %}
+                                    {% trans "This will invalidate all tickets in this order." %}
+                                </p>
+                            {% endif %}
+                            <a href="{% eventurl event 'presale:event.order.cancel' secret=order.secret order=order.code %}"
+                                    class="btn btn-danger">
+                                <span class="fa fa-remove"></span>
+                                {% trans "Cancel order" %}
+                            </a>
+                        {% else %}
+                            <p>
+                                {% blocktrans trimmed %}
+                                    You can cancel this order using the following button.
+                                {% endblocktrans %}
+                                {% trans "This will invalidate all tickets in this order." %}
+                            </p>
+                            <a href="{% eventurl event 'presale:event.order.cancel' secret=order.secret order=order.code %}"
+                                    class="btn btn-danger">
+                                <span class="fa fa-remove"></span>
+                                {% trans "Cancel order" %}
+                            </a>
+                        {% endif %}
+                    </li>
+                {% endif %}
+            </ul>
         </div>
     {% endif %}
 {% endblock %}
diff --git a/src/pretix/presale/templates/pretixpresale/event/order_change.html b/src/pretix/presale/templates/pretixpresale/event/order_change.html
new file mode 100644
index 0000000000..0734b144c1
--- /dev/null
+++ b/src/pretix/presale/templates/pretixpresale/event/order_change.html
@@ -0,0 +1,80 @@
+{% extends "pretixpresale/event/base.html" %}
+{% load i18n %}
+{% load bootstrap3 %}
+{% load rich_text %}
+{% block title %}{% trans "Modify order" %}{% endblock %}
+{% block content %}
+    <h2>
+        {% blocktrans trimmed with code=order.code %}
+            Change order: {{ code }}
+        {% endblocktrans %}
+    </h2>
+    <form method="post" href="">
+        {% csrf_token %}
+        {% for position, positions in formgroups.items %}
+            <div class="panel panel-default items">
+                <div class="panel-heading">
+                    <h3 class="panel-title">
+                        <strong>{{ position.item }}</strong>
+                        {% if position.variation %}
+                            – {{ position.variation }}
+                        {% endif %}
+                    </h3>
+                </div>
+                <div class="panel-body">
+                    <div class="form-order-change form-horizontal">
+                        {% if position.subevent %}
+                            <div class="form-group">
+                                <label class="col-md-3 control-label">
+                                    {% trans "Date" context "subevent" %}
+                                </label>
+                                <div class="col-md-9 form-control-text">
+                                    <ul class="addon-list">
+                                        {{ pos.subevent.name }} &middot; {{ pos.subevent.get_date_range_display }}
+                                        {% if pos.event.settings.show_times %}
+                                            <span class="fa fa-clock-o"></span>
+                                            {{ pos.subevent.date_from|date:"TIME_FORMAT" }}
+                                        {% endif %}
+                                    </ul>
+                                </div>
+                            </div>
+                        {% endif %}
+
+                        {% for p in positions %}
+                            {% if p.pk != position.pk %}
+                                {# Add-Ons #}
+                                <legend>+ {{ p.item.name }}{% if p.variation %} – {{ p.variation.value }}{% endif %}</legend>
+                            {% endif %}
+                            {% if p.attendee_name %}
+                                <div class="form-group">
+                                    <label class="col-md-3 control-label">
+                                        {% trans "Attendee name" %}
+                                    </label>
+                                    <div class="col-md-9 form-control-text">
+                                        {{ p.attendee_name }}
+                                    </div>
+                                </div>
+                            {% endif %}
+                            {% bootstrap_form p.form layout="checkout" %}
+                        {% endfor %}
+                    </div>
+                </div>
+            </div>
+        {% endfor %}
+
+        <div class="row checkout-button-row">
+            <div class="col-md-4">
+                <a class="btn btn-block btn-default btn-lg"
+                        href="{{ view.get_order_url }}">
+                    {% trans "Cancel" %}
+                </a>
+            </div>
+            <div class="col-md-4 col-md-offset-4">
+                <button class="btn btn-block btn-primary btn-lg" type="submit">
+                    {% trans "Save changes" %}
+                </button>
+            </div>
+            <div class="clearfix"></div>
+        </div>
+    </form>
+{% endblock %}
diff --git a/src/pretix/presale/urls.py b/src/pretix/presale/urls.py
index 8ba461afa2..dfb00db5df 100644
--- a/src/pretix/presale/urls.py
+++ b/src/pretix/presale/urls.py
@@ -64,6 +64,9 @@ event_patterns = [
     url(r'^order/(?P<order>[^/]+)/(?P<secret>[A-Za-z0-9]+)/invoice$',
         pretix.presale.views.order.OrderInvoiceCreate.as_view(),
         name='event.order.geninvoice'),
+    url(r'^order/(?P<order>[^/]+)/(?P<secret>[A-Za-z0-9]+)/change$',
+        pretix.presale.views.order.OrderChange.as_view(),
+        name='event.order.change'),
     url(r'^order/(?P<order>[^/]+)/(?P<secret>[A-Za-z0-9]+)/cancel$',
         pretix.presale.views.order.OrderCancel.as_view(),
         name='event.order.cancel'),
diff --git a/src/pretix/presale/views/order.py b/src/pretix/presale/views/order.py
index 3f00ffe953..4e8fdc5016 100644
--- a/src/pretix/presale/views/order.py
+++ b/src/pretix/presale/views/order.py
@@ -2,6 +2,7 @@ import inspect
 import mimetypes
 import os
 import re
+from collections import OrderedDict
 from decimal import Decimal
 
 from django import forms
@@ -25,7 +26,8 @@ from pretix.base.models import (
     CachedTicket, GiftCard, Invoice, Order, OrderPosition, Quota,
 )
 from pretix.base.models.orders import (
-    CachedCombinedTicket, OrderFee, OrderPayment, OrderRefund, QuestionAnswer,
+    CachedCombinedTicket, InvoiceAddress, OrderFee, OrderPayment, OrderRefund,
+    QuestionAnswer,
 )
 from pretix.base.payment import PaymentException
 from pretix.base.services.invoices import (
@@ -34,17 +36,20 @@ from pretix.base.services.invoices import (
 )
 from pretix.base.services.mail import SendMailException
 from pretix.base.services.orders import (
-    OrderError, cancel_order, change_payment_provider,
+    OrderChangeManager, OrderError, cancel_order, change_payment_provider,
 )
+from pretix.base.services.pricing import get_price
 from pretix.base.services.tickets import generate, invalidate_cache
 from pretix.base.signals import (
     allow_ticket_download, order_modified, register_ticket_outputs,
 )
+from pretix.base.templatetags.money import money_filter
 from pretix.base.views.mixins import OrderQuestionsViewMixin
 from pretix.base.views.tasks import AsyncAction
 from pretix.helpers.safedownload import check_token
 from pretix.multidomain.urlreverse import build_absolute_uri, eventreverse
 from pretix.presale.forms.checkout import InvoiceAddressForm, QuestionsForm
+from pretix.presale.forms.order import OrderPositionChangeForm
 from pretix.presale.views import (
     CartMixin, EventViewMixin, iframe_entry_view_wrapper,
 )
@@ -1006,3 +1011,131 @@ class InvoiceDownload(EventViewMixin, OrderDetailMixin, View):
         resp['Content-Disposition'] = 'inline; filename="{}.pdf"'.format(invoice.number)
         resp._csp_ignore = True  # Some browser's PDF readers do not work with CSP
         return resp
+
+
+@method_decorator(xframe_options_exempt, 'dispatch')
+class OrderChange(EventViewMixin, OrderDetailMixin, TemplateView):
+    template_name = "pretixpresale/event/order_change.html"
+
+    def dispatch(self, request, *args, **kwargs):
+        self.request = request
+        self.kwargs = kwargs
+        if not self.order:
+            raise Http404(_('Unknown order code or not authorized to access this order.'))
+        if not self.order.user_change_allowed:
+            messages.error(request, _('You cannot change this order.'))
+            return redirect(self.get_order_url())
+        return super().dispatch(request, *args, **kwargs)
+
+    @cached_property
+    def formdict(self):
+        storage = OrderedDict()
+        for pos in self.positions:
+            if pos.addon_to_id:
+                if pos.addon_to not in storage:
+                    storage[pos.addon_to] = []
+                storage[pos.addon_to].append(pos)
+            else:
+                if pos not in storage:
+                    storage[pos] = []
+                storage[pos].append(pos)
+        return storage
+
+    def get_context_data(self, **kwargs):
+        ctx = super().get_context_data(**kwargs)
+        ctx['order'] = self.order
+        ctx['positions'] = self.positions
+        ctx['formgroups'] = self.formdict
+        return ctx
+
+    @cached_property
+    def positions(self):
+        positions = list(
+            self.order.positions.select_related('item', 'item__tax_rule').prefetch_related(
+                'item__quotas', 'item__variations', 'item__variations__quotas'
+            )
+        )
+        try:
+            ia = self.order.invoice_address
+        except InvoiceAddress.DoesNotExist:
+            ia = None
+        for p in positions:
+            p.form = OrderPositionChangeForm(prefix='op-{}'.format(p.pk), instance=p,
+                                             invoice_address=ia, event=self.request.event,
+                                             data=self.request.POST if self.request.method == "POST" else None)
+        return positions
+
+    def _process_change(self, ocm):
+        try:
+            ia = self.order.invoice_address
+        except InvoiceAddress.DoesNotExist:
+            ia = None
+        for p in self.positions:
+            if not p.form.is_valid():
+                return False
+
+            try:
+                change_item = None
+                if p.form.cleaned_data['itemvar']:
+                    if '-' in p.form.cleaned_data['itemvar']:
+                        itemid, varid = p.form.cleaned_data['itemvar'].split('-')
+                    else:
+                        itemid, varid = p.form.cleaned_data['itemvar'], None
+
+                    item = self.request.event.items.get(pk=itemid)
+                    if varid:
+                        variation = item.variations.get(pk=varid)
+                    else:
+                        variation = None
+                    if item != p.item or variation != p.variation:
+                        change_item = (item, variation)
+
+                if change_item is not None:
+                    ocm.change_item(p, *change_item)
+                    new_price = get_price(change_item[0], change_item[1], voucher=p.voucher, subevent=p.subevent,
+                                          invoice_address=ia)
+
+                    if new_price.gross != p.price or new_price.rate != p.tax_rate:
+                        ocm.change_price(p, new_price.gross)
+
+                    if change_item[0].tax_rule != p.tax_rule or new_price.rate != p.tax_rate:
+                        ocm.change_tax_rule(p, change_item[0].tax_rule)
+
+            except OrderError as e:
+                p.custom_error = str(e)
+                return False
+        return True
+
+    def post(self, *args, **kwargs):
+        was_paid = self.order.status == Order.STATUS_PAID
+        ocm = OrderChangeManager(
+            self.order,
+            user=self.request.user,
+            notify=True,
+            reissue_invoice=True,
+        )
+        form_valid = self._process_change(ocm)
+
+        if not form_valid:
+            messages.error(self.request, _('An error occurred. Please see the details below.'))
+        else:
+            try:
+                ocm.commit(check_quotas=True)
+            except OrderError as e:
+                messages.error(self.request, str(e))
+            else:
+
+                if self.order.status != Order.STATUS_PAID and was_paid:
+                    messages.success(self.request, _('The order has been changed. You can now proceed by paying the open amount of {amount}.').format(
+                        amount=money_filter(self.order.pending_sum, self.request.event.currency)
+                    ))
+                    return redirect(eventreverse(self.request.event, 'presale:event.order.pay.change', kwargs={
+                        'order': self.order.code,
+                        'secret': self.order.secret
+                    }))
+                else:
+                    messages.success(self.request, _('The order has been changed.'))
+
+                return redirect(self.get_order_url())
+
+        return self.get(*args, **kwargs)
diff --git a/src/tests/base/test_models.py b/src/tests/base/test_models.py
index 24f9fb6308..004609756b 100644
--- a/src/tests/base/test_models.py
+++ b/src/tests/base/test_models.py
@@ -1319,47 +1319,6 @@ class OrderTestCase(BaseQuotaTestCase):
         assert self.order.user_cancel_deadline < now()
         assert not self.order.user_cancel_allowed
 
-    @classscope(attr='o')
-    def test_user_cancel_absolute_deadline_paid_no_subevents(self):
-        self.order.status = Order.STATUS_PAID
-        self.order.save()
-        self.event.settings.cancel_allow_user_paid = True
-        assert self.order.user_cancel_deadline is None
-        self.event.settings.set('cancel_allow_user_paid_until', RelativeDateWrapper(
-            now() + timedelta(days=1)
-        ))
-        self.order = Order.objects.get(pk=self.order.pk)
-        assert self.order.user_cancel_allowed
-        assert self.order.user_cancel_deadline > now()
-        self.event.settings.set('cancel_allow_user_paid_until', RelativeDateWrapper(
-            now() - timedelta(days=1)
-        ))
-        self.order = Order.objects.get(pk=self.order.pk)
-        assert self.order.user_cancel_deadline < now()
-        assert not self.order.user_cancel_allowed
-
-    @classscope(attr='o')
-    def test_user_cancel_relative_deadline_paid_no_subevents(self):
-        self.order.status = Order.STATUS_PAID
-        self.order.save()
-        self.event.date_from = now() + timedelta(days=3)
-        self.event.save()
-        self.event.settings.cancel_allow_user_paid = True
-
-        assert self.order.user_cancel_deadline is None
-        self.event.settings.set('cancel_allow_user_paid_until', RelativeDateWrapper(
-            RelativeDate(days_before=2, time=datetime.time(14, 0, 0), base_date_name='date_from')
-        ))
-        self.order = Order.objects.get(pk=self.order.pk)
-        assert self.order.user_cancel_deadline > now()
-        assert self.order.user_cancel_allowed
-        self.event.settings.set('cancel_allow_user_paid_until', RelativeDateWrapper(
-            RelativeDate(days_before=4, time=datetime.time(14, 0, 0), base_date_name='date_from')
-        ))
-        self.order = Order.objects.get(pk=self.order.pk)
-        assert self.order.user_cancel_deadline < now()
-        assert not self.order.user_cancel_allowed
-
     @classscope(attr='o')
     def test_user_cancel_relative_deadline_to_subevents(self):
         self.event.date_from = now() + timedelta(days=3)
@@ -1595,6 +1554,180 @@ class OrderTestCase(BaseQuotaTestCase):
             p2: Decimal('10.00'),
         }
 
+    @classscope(attr='o')
+    def test_can_change_order(self):
+        item1 = Item.objects.create(event=self.event, name="Ticket", default_price=23,
+                                    admission=True, allow_cancel=True)
+        v = item1.variations.create(value="V")
+        OrderPosition.objects.create(order=self.order, item=item1,
+                                     variation=v, price=23)
+        assert not self.order.user_change_allowed
+        self.event.settings.change_allow_user_variation = True
+        assert self.order.user_change_allowed
+
+    @classscope(attr='o')
+    def test_can_change_order_with_giftcard(self):
+        item1 = Item.objects.create(event=self.event, name="Ticket", default_price=23,
+                                    admission=True, allow_cancel=True, issue_giftcard=True)
+        v = item1.variations.create(value="V")
+        p = OrderPosition.objects.create(order=self.order, item=item1,
+                                         variation=v, price=23)
+        self.event.settings.change_allow_user_variation = True
+        self.event.organizer.issued_gift_cards.create(
+            currency="EUR", issued_in=p
+        )
+        assert not self.order.user_change_allowed
+
+    @classscope(attr='o')
+    def test_can_change_checked_in(self):
+        v = self.item1.variations.create(value="V")
+        self.order.positions.update(variation=v)
+        self.order.status = Order.STATUS_PAID
+        self.order.save()
+        self.event.settings.change_allow_user_variation = True
+        assert self.order.user_change_allowed
+        Checkin.objects.create(
+            position=self.order.positions.first(),
+            list=CheckinList.objects.create(event=self.event, name='Default')
+        )
+        assert not self.order.user_change_allowed
+
+    @classscope(attr='o')
+    def test_can_change_order_multiple(self):
+        item1 = Item.objects.create(event=self.event, name="Ticket", default_price=23,
+                                    admission=True, allow_cancel=True)
+        v = item1.variations.create(value="V")
+        item2 = Item.objects.create(event=self.event, name="Ticket", default_price=23,
+                                    admission=True, allow_cancel=True)
+        v2 = item2.variations.create(value="V")
+        OrderPosition.objects.create(order=self.order, item=item1,
+                                     variation=v, price=23)
+        OrderPosition.objects.create(order=self.order, item=item2,
+                                     variation=v2, price=23)
+        self.event.settings.change_allow_user_variation = True
+        assert self.order.user_change_allowed
+
+    @classscope(attr='o')
+    def test_can_not_change_order(self):
+        item1 = Item.objects.create(event=self.event, name="Ticket", default_price=23,
+                                    admission=True, allow_cancel=False)
+        v = item1.variations.create(value="V")
+        OrderPosition.objects.create(order=self.order, item=item1,
+                                     variation=v, price=23)
+        self.event.settings.change_allow_user_variation = True
+        assert self.order.user_change_allowed is False
+
+    @classscope(attr='o')
+    def test_require_any_variation(self):
+        item1 = Item.objects.create(event=self.event, name="Ticket", default_price=23,
+                                    admission=True, allow_cancel=True)
+        OrderPosition.objects.create(order=self.order, item=item1,
+                                     variation=None, price=23)
+        self.event.settings.change_allow_user_variation = True
+        assert self.order.user_change_allowed is False
+        item2 = Item.objects.create(event=self.event, name="Ticket", default_price=23,
+                                    admission=True, allow_cancel=True)
+        v2 = item2.variations.create(value="V")
+        OrderPosition.objects.create(order=self.order, item=item2,
+                                     variation=v2, price=23)
+        assert self.order.user_change_allowed is True
+
+    @classscope(attr='o')
+    def test_can_not_change_order_multiple(self):
+        item1 = Item.objects.create(event=self.event, name="Ticket", default_price=23,
+                                    admission=True, allow_cancel=False)
+        item2 = Item.objects.create(event=self.event, name="Ticket", default_price=23,
+                                    admission=True, allow_cancel=True)
+        v = item1.variations.create(value="V")
+        v2 = item2.variations.create(value="V")
+        OrderPosition.objects.create(order=self.order, item=item1,
+                                     variation=v, price=23)
+        OrderPosition.objects.create(order=self.order, item=item2,
+                                     variation=v2, price=23)
+        self.event.settings.change_allow_user_variation = True
+        assert self.order.user_change_allowed is False
+
+    @classscope(attr='o')
+    def test_can_not_change_order_multiple_mixed(self):
+        item1 = Item.objects.create(event=self.event, name="Ticket", default_price=23,
+                                    admission=True, allow_cancel=False)
+        item2 = Item.objects.create(event=self.event, name="Ticket", default_price=23,
+                                    admission=True, allow_cancel=True)
+        v = item1.variations.create(value="V")
+        v2 = item2.variations.create(value="V")
+        OrderPosition.objects.create(order=self.order, item=item1,
+                                     variation=v, price=23)
+        OrderPosition.objects.create(order=self.order, item=item2,
+                                     variation=v2, price=23)
+        self.event.settings.change_allow_user_variation = True
+        assert self.order.user_change_allowed is False
+
+    @classscope(attr='o')
+    def test_user_change_absolute_deadline_unpaid_no_subevents(self):
+        v = self.item1.variations.create(value="V")
+        self.order.positions.update(variation=v)
+        self.event.settings.change_allow_user_variation = True
+        assert self.order.user_change_deadline is None
+        self.event.settings.set('change_allow_user_until', RelativeDateWrapper(
+            now() + timedelta(days=1)
+        ))
+        self.order = Order.objects.get(pk=self.order.pk)
+        assert self.order.user_change_deadline > now()
+        assert self.order.user_change_allowed
+        self.event.settings.set('change_allow_user_until', RelativeDateWrapper(
+            now() - timedelta(days=1)
+        ))
+        self.order = Order.objects.get(pk=self.order.pk)
+        assert self.order.user_change_deadline < now()
+        assert not self.order.user_change_allowed
+
+    @classscope(attr='o')
+    def test_user_change_relative_deadline_unpaid_no_subevents(self):
+        v = self.item1.variations.create(value="V")
+        self.order.positions.update(variation=v)
+        self.event.settings.change_allow_user_variation = True
+        self.event.date_from = now() + timedelta(days=3)
+        self.event.save()
+
+        assert self.order.user_change_deadline is None
+        self.event.settings.set('change_allow_user_until', RelativeDateWrapper(
+            RelativeDate(days_before=2, time=datetime.time(14, 0, 0), base_date_name='date_from')
+        ))
+        self.order = Order.objects.get(pk=self.order.pk)
+        assert self.order.user_change_deadline > now()
+        assert self.order.user_change_allowed
+        self.event.settings.set('change_allow_user_until', RelativeDateWrapper(
+            RelativeDate(days_before=4, time=datetime.time(14, 0, 0), base_date_name='date_from')
+        ))
+        self.order = Order.objects.get(pk=self.order.pk)
+        assert self.order.user_change_deadline < now()
+        assert not self.order.user_change_allowed
+
+    @classscope(attr='o')
+    def test_user_change_relative_deadline_to_subevents(self):
+        v = self.item1.variations.create(value="V")
+        self.order.positions.update(variation=v)
+        self.event.settings.change_allow_user_variation = True
+        self.event.date_from = now() + timedelta(days=3)
+        self.event.has_subevents = True
+        self.event.save()
+        se1 = self.event.subevents.create(name="SE1", date_from=now() + timedelta(days=10))
+        se2 = self.event.subevents.create(name="SE2", date_from=now() + timedelta(days=1))
+        self.op1.subevent = se1
+        self.op1.save()
+        self.op2.subevent = se2
+        self.op2.save()
+
+        self.event.settings.set('change_allow_user_until', RelativeDateWrapper(
+            RelativeDate(days_before=2, time=datetime.time(14, 0, 0), base_date_name='date_from')
+        ))
+        self.order = Order.objects.get(pk=self.order.pk)
+        assert self.order.user_change_deadline < now()
+        self.op2.subevent = se1
+        self.op2.save()
+        self.order = Order.objects.get(pk=self.order.pk)
+        assert self.order.user_change_deadline > now()
+
 
 class ItemCategoryTest(TestCase):
     """
diff --git a/src/tests/presale/test_orders.py b/src/tests/presale/test_orders.py
index 07a9df9304..475d12b767 100644
--- a/src/tests/presale/test_orders.py
+++ b/src/tests/presale/test_orders.py
@@ -37,9 +37,9 @@ class BaseOrdersTest(TestCase):
         self.shirt = Item.objects.create(event=self.event, name='T-Shirt', category=self.category, default_price=12)
         self.quota_shirts.items.add(self.shirt)
         self.shirt_red = ItemVariation.objects.create(item=self.shirt, default_price=14, value="Red")
-        var2 = ItemVariation.objects.create(item=self.shirt, value="Blue")
+        self.shirt_blue = ItemVariation.objects.create(item=self.shirt, value="Blue")
         self.quota_shirts.variations.add(self.shirt_red)
-        self.quota_shirts.variations.add(var2)
+        self.quota_shirts.variations.add(self.shirt_blue)
         self.quota_tickets = Quota.objects.create(event=self.event, name='Tickets', size=5)
         self.ticket = Item.objects.create(event=self.event, name='Early-bird ticket',
                                           category=self.category, default_price=23,
@@ -1290,3 +1290,214 @@ class OrdersTest(BaseOrdersTest):
                                                         self.order.secret, a.pk, match.group(1))
         )
         assert response.status_code == 404
+
+    def test_change_not_allowed(self):
+        response = self.client.get(
+            '/%s/%s/order/%s/%s/change' % (self.orga.slug, self.event.slug, self.order.code, self.order.secret)
+        )
+        assert response.status_code == 302
+
+    def test_change_variation_paid(self):
+        self.event.settings.change_allow_user_variation = True
+        self.event.settings.change_allow_user_price = 'any'
+
+        with scopes_disabled():
+            shirt_pos = OrderPosition.objects.create(
+                order=self.order,
+                item=self.shirt,
+                variation=self.shirt_red,
+                price=Decimal("14"),
+            )
+        response = self.client.get(
+            '/%s/%s/order/%s/%s/change' % (self.orga.slug, self.event.slug, self.order.code, self.order.secret)
+        )
+        assert response.status_code == 200
+        response = self.client.post(
+            '/%s/%s/order/%s/%s/change' % (self.orga.slug, self.event.slug, self.order.code, self.order.secret), {
+                f'op-{shirt_pos.pk}-itemvar': f'{self.shirt.pk}-{self.shirt_blue.pk}',
+                f'op-{self.ticket_pos.pk}-itemvar': f'{self.ticket.pk}',
+            }, follow=True)
+        self.assertRedirects(response,
+                             '/%s/%s/order/%s/%s/' % (self.orga.slug, self.event.slug, self.order.code,
+                                                      self.order.secret),
+                             target_status_code=200)
+        shirt_pos.refresh_from_db()
+        assert shirt_pos.variation == self.shirt_blue
+        assert shirt_pos.price == Decimal('12.00')
+        self.order.refresh_from_db()
+        assert self.order.status == Order.STATUS_PENDING
+        assert self.order.total == Decimal('35.00')
+
+    def test_change_variation_require_higher_price(self):
+        self.event.settings.change_allow_user_variation = True
+        self.event.settings.change_allow_user_price = 'gt'
+
+        with scopes_disabled():
+            shirt_pos = OrderPosition.objects.create(
+                order=self.order,
+                item=self.shirt,
+                variation=self.shirt_red,
+                price=Decimal("14"),
+            )
+        response = self.client.get(
+            '/%s/%s/order/%s/%s/change' % (self.orga.slug, self.event.slug, self.order.code, self.order.secret)
+        )
+        assert response.status_code == 200
+        response = self.client.post(
+            '/%s/%s/order/%s/%s/change' % (self.orga.slug, self.event.slug, self.order.code, self.order.secret), {
+                f'op-{shirt_pos.pk}-itemvar': f'{self.shirt.pk}-{self.shirt_blue.pk}',
+                f'op-{self.ticket_pos.pk}-itemvar': f'{self.ticket.pk}',
+            }, follow=True)
+        assert response.status_code == 200
+        assert 'alert-danger' in response.rendered_content
+
+        shirt_pos.variation = self.shirt_blue
+        shirt_pos.price = Decimal('12.00')
+        shirt_pos.save()
+
+        response = self.client.post(
+            '/%s/%s/order/%s/%s/change' % (self.orga.slug, self.event.slug, self.order.code, self.order.secret),
+            {
+                f'op-{shirt_pos.pk}-itemvar': f'{self.shirt.pk}-{self.shirt_red.pk}',
+                f'op-{self.ticket_pos.pk}-itemvar': f'{self.ticket.pk}',
+            },
+            follow=True
+        )
+        self.assertRedirects(response,
+                             '/%s/%s/order/%s/%s/' % (self.orga.slug, self.event.slug, self.order.code,
+                                                      self.order.secret),
+                             target_status_code=200)
+        shirt_pos.refresh_from_db()
+        assert shirt_pos.variation == self.shirt_red
+        assert shirt_pos.price == Decimal('14.00')
+        self.order.refresh_from_db()
+        assert self.order.status == Order.STATUS_PENDING
+        assert self.order.total == Decimal('37.00')
+
+    def test_change_variation_require_equal_price(self):
+        self.event.settings.change_allow_user_variation = True
+        self.event.settings.change_allow_user_price = 'eq'
+
+        with scopes_disabled():
+            shirt_pos = OrderPosition.objects.create(
+                order=self.order,
+                item=self.shirt,
+                variation=self.shirt_blue,
+                price=Decimal("12"),
+            )
+        response = self.client.get(
+            '/%s/%s/order/%s/%s/change' % (self.orga.slug, self.event.slug, self.order.code, self.order.secret)
+        )
+        assert response.status_code == 200
+        response = self.client.post(
+            '/%s/%s/order/%s/%s/change' % (self.orga.slug, self.event.slug, self.order.code, self.order.secret), {
+                f'op-{shirt_pos.pk}-itemvar': f'{self.shirt.pk}-{self.shirt_red.pk}',
+                f'op-{self.ticket_pos.pk}-itemvar': f'{self.ticket.pk}',
+            }, follow=True)
+        assert response.status_code == 200
+        assert 'alert-danger' in response.rendered_content
+
+    def test_change_variation_require_same_product(self):
+        self.event.settings.change_allow_user_variation = True
+        self.event.settings.change_allow_user_price = 'any'
+
+        with scopes_disabled():
+            shirt_pos = OrderPosition.objects.create(
+                order=self.order,
+                item=self.shirt,
+                variation=self.shirt_blue,
+                price=Decimal("12"),
+            )
+        response = self.client.get(
+            '/%s/%s/order/%s/%s/change' % (self.orga.slug, self.event.slug, self.order.code, self.order.secret)
+        )
+        assert response.status_code == 200
+        response = self.client.post(
+            '/%s/%s/order/%s/%s/change' % (self.orga.slug, self.event.slug, self.order.code, self.order.secret), {
+                f'op-{shirt_pos.pk}-itemvar': f'{self.ticket.pk}',
+                f'op-{self.ticket_pos.pk}-itemvar': f'{self.ticket.pk}',
+            }, follow=True)
+        assert response.status_code == 200
+        assert 'alert-danger' in response.rendered_content
+
+    def test_change_variation_require_quota(self):
+        self.event.settings.change_allow_user_variation = True
+        self.event.settings.change_allow_user_price = 'any'
+
+        with scopes_disabled():
+            q = self.event.quotas.create(name="s2", size=0)
+            q.items.add(self.shirt)
+            q.variations.add(self.shirt_red)
+
+        with scopes_disabled():
+            shirt_pos = OrderPosition.objects.create(
+                order=self.order,
+                item=self.shirt,
+                variation=self.shirt_blue,
+                price=Decimal("12"),
+            )
+        response = self.client.get(
+            '/%s/%s/order/%s/%s/change' % (self.orga.slug, self.event.slug, self.order.code, self.order.secret)
+        )
+        assert response.status_code == 200
+        response = self.client.post(
+            '/%s/%s/order/%s/%s/change' % (self.orga.slug, self.event.slug, self.order.code, self.order.secret), {
+                f'op-{shirt_pos.pk}-itemvar': f'{self.shirt.pk}-{self.shirt_red.pk}',
+                f'op-{self.ticket_pos.pk}-itemvar': f'{self.ticket.pk}',
+            }, follow=True)
+        assert response.status_code == 200
+        assert 'alert-danger' in response.rendered_content
+
+        q.variations.add(self.shirt_blue)
+
+        response = self.client.post(
+            '/%s/%s/order/%s/%s/change' % (self.orga.slug, self.event.slug, self.order.code, self.order.secret), {
+                f'op-{shirt_pos.pk}-itemvar': f'{self.shirt.pk}-{self.shirt_red.pk}',
+                f'op-{self.ticket_pos.pk}-itemvar': f'{self.ticket.pk}',
+            }, follow=True)
+        self.assertRedirects(response,
+                             '/%s/%s/order/%s/%s/' % (self.orga.slug, self.event.slug, self.order.code,
+                                                      self.order.secret),
+                             target_status_code=200)
+        shirt_pos.refresh_from_db()
+        assert shirt_pos.variation == self.shirt_red
+        assert shirt_pos.price == Decimal('14.00')
+
+    def test_change_paid_to_pending(self):
+        self.event.settings.change_allow_user_variation = True
+        self.event.settings.change_allow_user_price = 'any'
+        self.order.status = Order.STATUS_PAID
+        self.order.save()
+
+        with scopes_disabled():
+            self.order.payments.create(provider="manual", amount=Decimal('35.00'), state=OrderPayment.PAYMENT_STATE_CONFIRMED)
+            shirt_pos = OrderPosition.objects.create(
+                order=self.order,
+                item=self.shirt,
+                variation=self.shirt_blue,
+                price=Decimal("12"),
+            )
+
+        response = self.client.get(
+            '/%s/%s/order/%s/%s/change' % (self.orga.slug, self.event.slug, self.order.code, self.order.secret)
+        )
+        assert response.status_code == 200
+        response = self.client.post(
+            '/%s/%s/order/%s/%s/change' % (self.orga.slug, self.event.slug, self.order.code, self.order.secret),
+            {
+                f'op-{shirt_pos.pk}-itemvar': f'{self.shirt.pk}-{self.shirt_red.pk}',
+                f'op-{self.ticket_pos.pk}-itemvar': f'{self.ticket.pk}',
+            },
+            follow=True
+        )
+        self.assertRedirects(response,
+                             '/%s/%s/order/%s/%s/pay/change' % (self.orga.slug, self.event.slug, self.order.code,
+                                                                self.order.secret),
+                             target_status_code=200)
+        assert 'The order has been changed. You can now proceed by paying the open amount of €2.00.' in response.rendered_content
+        shirt_pos.refresh_from_db()
+        assert shirt_pos.variation == self.shirt_red
+        assert shirt_pos.price == Decimal('14.00')
+        self.order.refresh_from_db()
+        assert self.order.status == Order.STATUS_PENDING
+        assert self.order.pending_sum == Decimal('2.00')