Fix handling of inbound prices

doc/api/resources/orders.rst

@@ -1029,6 +1029,7 @@ Creating orders
      charge will be created), this is just informative in case you *handled the payment already*.
    * ``payment_date`` (optional) – Date and time of the completion of the payment.
    * ``tax_rounding_mode`` (optional)
+   * ``total`` (optional, will be computed from backend and operation will fail if the computation has a different result)
    * ``comment`` (optional)
    * ``custom_followup_at`` (optional)
    * ``checkin_attention`` (optional)
@@ -1059,6 +1060,9 @@ Creating orders
       * ``item``
       * ``variation`` (optional)
       * ``price`` (optional, if set to ``null`` or missing the price will be computed from the given product)
+      * ``tax_rule`` (optional, if set to ``null`` or missing the tax rule will be selected from the given product)
+      * ``tax_rate`` (optional, only works together with a tax rule, if set to ``null`` or missing the tax rate will be computed from the given tax rule)
+      * ``tax_code`` (optional, only works together with a tax rule, if set to ``null`` or missing the tax code will be computed from the given tax rule)
       * ``seat`` (The ``seat_guid`` attribute of a seat. Required when the specified ``item`` requires a seat, otherwise must be ``null``.)
       * ``attendee_name`` **or** ``attendee_name_parts`` (optional)
       * ``voucher`` (optional, the ``code`` attribute of a valid voucher)

pyproject.toml

@@ -61,6 +61,7 @@ dependencies = [
   "dnspython==2.8.*",
   "drf_ujson2==1.7.*",
   "geoip2==5.*",
+  "importlib_metadata==9.*",  # Polyfill, we can probably drop this once we require Python 3.10+
   "isoweek",
   "jsonschema",
   "kombu==5.6.*",

src/pretix/api/serializers/order.py

@@ -607,7 +607,6 @@ class OrderPositionSerializer(I18nAwareModelSerializer):
         fields = ('id', 'order', 'positionid', 'item', 'variation', 'price', 'attendee_name', 'attendee_name_parts',
                   'company', 'street', 'zipcode', 'city', 'country', 'state', 'discount',
                   'attendee_email', 'voucher', 'tax_rate', 'tax_value', 'secret', 'addon_to', 'subevent', 'checkins',
-                  'print_logs', 'downloads', 'answers', 'tax_rule', 'pseudonymization_id', 'pdf_data', 'seat', 'canceled',
                   'print_logs', 'downloads', 'answers', 'tax_rule', 'tax_code', 'pseudonymization_id', 'pdf_data', 'seat',
                   'canceled', 'valid_from', 'valid_until', 'blocked', 'voucher_budget_use', 'plugin_data')
         read_only_fields = (
@@ -1027,18 +1026,56 @@ class OrderFeeCreateSerializer(I18nAwareModelSerializer):
     _treat_value_as_percentage = serializers.BooleanField(default=False, required=False)
     _split_taxes_like_products = serializers.BooleanField(default=False, required=False)
 
+    tax_rate = serializers.DecimalField(required=False, decimal_places=4, max_digits=7)
+    tax_value = serializers.DecimalField(required=False, decimal_places=2, max_digits=13)
+    value_includes_rounding_correction = serializers.DecimalField(required=False, decimal_places=2, max_digits=13)
+    tax_value_includes_rounding_correction = serializers.DecimalField(required=False, decimal_places=2, max_digits=13)
+
     class Meta:
         model = OrderFee
-        fields = ('fee_type', 'value', 'description', 'internal_type', 'tax_rule',
-                  '_treat_value_as_percentage', '_split_taxes_like_products')
+        fields = (
+            'fee_type', 'value', 'description', 'internal_type', 'tax_rule',
+            '_treat_value_as_percentage', '_split_taxes_like_products',
+            # The following fields should usually not be set by the client but computed by the backend. However, it makes
+            # sense to set them when the decision on the tax rate is made irrevertably on the client side, such as with
+            # pretixPOS.
+            'tax_rate', 'tax_code',
+            # The following fields are undocumented and only used by pretixPOS. They do *NOT* override the calculations
+            # by the backends but are checked against them and must match exactly, otherwise the entire operation is
+            # aborted to avoid diverging tax values between POS reports and backend reports.
+            'tax_value', 'value_includes_rounding_correction', 'tax_value_includes_rounding_correction',
+        )
 
     def validate_tax_rule(self, tr):
         if tr and tr.event != self.context['event']:
             raise ValidationError(
-                'The specified tax rate does not belong to this event.'
+                'The specified tax rule does not belong to this event.'
             )
         return tr
 
+    def validate(self, attrs):
+        if attrs.get('_treat_value_as_percentage'):
+            for k in ('tax_value', 'value_includes_rounding_correction', 'tax_value_includes_rounding_correction'):
+                if k in attrs:
+                    raise ValidationError({
+                        k: ['You cannot ask for the value to be treated as a percentage if you already computed taxes.']
+                    })
+        if attrs.get('_split_taxes_like_products'):
+            for k in ('tax_rate', 'tax_value', 'value_includes_rounding_correction', 'tax_value_includes_rounding_correction'):
+                if k in attrs:
+                    raise ValidationError({
+                        k: ['You cannot ask for the value to be distributed over tax rates if you already set the tax rate or computed taxes.']
+                    })
+        if 'tax_rate' in attrs and 'tax_rule' not in attrs:
+            raise ValidationError({
+                'tax_rate': ['Tax rate cannot be stored without tax rule.']
+            })
+
+        if 'value_includes_rounding_correction' in attrs:
+            # Make all computations like discounts on the price before rounding, later compare against rounding again
+            attrs['value'] = attrs['value'] - attrs['value_includes_rounding_correction']
+        return attrs
+
 
 class OrderPositionCreateSerializer(I18nAwareModelSerializer):
     answers = AnswerCreateSerializer(many=True, required=False)
@@ -1054,13 +1091,27 @@ class OrderPositionCreateSerializer(I18nAwareModelSerializer):
     requested_valid_from = serializers.DateTimeField(required=False, allow_null=True)
     use_reusable_medium = serializers.PrimaryKeyRelatedField(queryset=ReusableMedium.objects.none(),
                                                              required=False, allow_null=True)
+    tax_rate = serializers.DecimalField(required=False, decimal_places=4, max_digits=7)
+    tax_value = serializers.DecimalField(required=False, decimal_places=2, max_digits=13)
+    price_includes_rounding_correction = serializers.DecimalField(required=False, decimal_places=2, max_digits=13)
+    tax_value_includes_rounding_correction = serializers.DecimalField(required=False, decimal_places=2, max_digits=13)
 
     class Meta:
         model = OrderPosition
-        fields = ('positionid', 'item', 'variation', 'price', 'attendee_name', 'attendee_name_parts', 'attendee_email',
-                  'company', 'street', 'zipcode', 'city', 'country', 'state', 'is_bundled',
-                  'secret', 'addon_to', 'subevent', 'answers', 'seat', 'voucher', 'valid_from', 'valid_until',
-                  'requested_valid_from', 'use_reusable_medium', 'discount')
+        fields = (
+            'positionid', 'item', 'variation', 'price', 'attendee_name', 'attendee_name_parts', 'attendee_email',
+            'company', 'street', 'zipcode', 'city', 'country', 'state', 'is_bundled',
+            'secret', 'addon_to', 'subevent', 'answers', 'seat', 'voucher', 'valid_from', 'valid_until',
+            'requested_valid_from', 'use_reusable_medium', 'discount',
+            # The following fields should usually not be set by the client but computed by the backend. However, it makes
+            # sense to set them when the decision on the tax rate is made irrevertably on the client side, such as with
+            # pretixPOS.
+            'tax_rule', 'tax_rate', 'tax_code',
+            # The following fields are undocumented and only used by pretixPOS. They do *NOT* override the calculations
+            # by the backends but are checked against them and must match exactly, otherwise the entire operation is
+            # aborted to avoid diverging tax values between POS reports and backend reports.
+            'tax_value', 'price_includes_rounding_correction', 'tax_value_includes_rounding_correction',
+        )
 
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
@@ -1098,6 +1149,13 @@ class OrderPositionCreateSerializer(I18nAwareModelSerializer):
             )
         return item
 
+    def validate_tax_rule(self, tax_rule):
+        if tax_rule.event != self.context['event']:
+            raise ValidationError(
+                'The specified tax rule does not belong to this event.'
+            )
+        return tax_rule
+
     def validate_subevent(self, subevent):
         if self.context['event'].has_subevents:
             if not subevent:
@@ -1161,6 +1219,15 @@ class OrderPositionCreateSerializer(I18nAwareModelSerializer):
                 {'discount': ['You can only specify a discount if you do the price computation, but price is not set.']}
             )
 
+        if 'tax_rate' in data and 'tax_rule' not in data and not data['item'].tax_rule_id:
+            raise ValidationError({
+                'tax_rate': ['Tax rate cannot be stored without tax rule.']
+            })
+
+        if 'price_includes_rounding_correction' in data:
+            # Make all computations like discounts on the price before rounding, later compare against rounding again
+            data['price'] = data['price'] - data['price_includes_rounding_correction']
+
         return data
 
 
@@ -1218,6 +1285,7 @@ class OrderCreateSerializer(I18nAwareModelSerializer):
     tax_rounding_mode = serializers.ChoiceField(choices=ROUNDING_MODES, allow_null=True, required=False,)
     locale = serializers.ChoiceField(choices=[], required=False, allow_null=True)
     use_gift_cards = serializers.ListField(child=serializers.CharField(required=False), required=False)
+    total = serializers.DecimalField(required=False, decimal_places=2, max_digits=13)
 
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
@@ -1232,7 +1300,7 @@ class OrderCreateSerializer(I18nAwareModelSerializer):
         model = Order
         fields = ('code', 'status', 'testmode', 'email', 'phone', 'locale', 'payment_provider', 'fees', 'comment', 'sales_channel',
                   'invoice_address', 'positions', 'checkin_attention', 'checkin_text', 'payment_info', 'payment_date',
-                  'consume_carts', 'force', 'send_email', 'simulate', 'customer', 'custom_followup_at',
+                  'consume_carts', 'force', 'send_email', 'simulate', 'customer', 'custom_followup_at', 'total',
                   'require_approval', 'valid_if_pending', 'expires', 'api_meta', 'tax_rounding_mode', 'use_gift_cards')
 
     def validate_payment_provider(self, pp):
@@ -1572,6 +1640,7 @@ class OrderCreateSerializer(I18nAwareModelSerializer):
         if validated_data.get('locale', None) is None:
             validated_data['locale'] = self.context['event'].settings.locale
 
+        expected_total = validated_data.pop('total', None)
         order = Order(event=self.context['event'], **validated_data)
         if not validated_data.get('expires'):
             order.set_expires(subevents=[p.get('subevent') for p in positions_data])
@@ -1603,7 +1672,14 @@ class OrderCreateSerializer(I18nAwareModelSerializer):
                 pos_data['attendee_name_parts'] = {
                     '_legacy': attendee_name
                 }
-            pos = OrderPosition(**{k: v for k, v in pos_data.items() if k not in ('answers', '_quotas', 'use_reusable_medium')})
+            pos = OrderPosition(**{k: v for k, v in pos_data.items() if k not in (
+                'answers',
+                '_quotas',
+                'use_reusable_medium',
+                'tax_value',
+                'price_includes_rounding_correction',
+                'tax_value_includes_rounding_correction',
+            )})
             if simulate:
                 pos.order = order._wrapped
             else:
@@ -1646,7 +1722,12 @@ class OrderCreateSerializer(I18nAwareModelSerializer):
                     if not pos.item.tax_rule or pos.item.tax_rule.price_includes_tax:
                         price_after_voucher = max(pos.price, pos.voucher.calculate_price(listed_price))
                     else:
-                        pos._calculate_tax(invoice_address=ia)
+                        pos._calculate_tax(
+                            invoice_address=ia,
+                            tax_rule=pos_data.get('tax_rule'),
+                            override_tax_rate=pos_data.get('tax_rate'),
+                            override_tax_code=pos_data.get('tax_code'),
+                        )
                         price_after_voucher = max(pos.price - pos.tax_value, pos.voucher.calculate_price(listed_price))
                 else:
                     price_after_voucher = listed_price
@@ -1678,7 +1759,12 @@ class OrderCreateSerializer(I18nAwareModelSerializer):
             answers_data = pos_data.pop('answers', [])
             use_reusable_medium = pos_data.pop('use_reusable_medium', None)
             pos = pos_data['__instance']
-            pos._calculate_tax(invoice_address=ia)
+            pos._calculate_tax(
+                invoice_address=ia,
+                tax_rule=pos_data.get('tax_rule', None),
+                override_tax_rate=pos_data.get('tax_rate'),
+                override_tax_code=pos_data.get('tax_code'),
+            )
 
             if simulate:
                 pos = WrappedModel(pos)
@@ -1777,7 +1863,11 @@ class OrderCreateSerializer(I18nAwareModelSerializer):
                 for tr, val in fee_values:
                     fee_data['tax_rule'] = tr
                     fee_data['value'] = val
-                    f = OrderFee(**fee_data)
+                    f = OrderFee(**{k: v for k, v in fee_data.items() if k not in (
+                        'tax_value',
+                        'value_includes_rounding_correction',
+                        'tax_value_includes_rounding_correction'
+                    )})
                     f.order = order._wrapped if simulate else order
                     f._calculate_tax()
                     fees.append(f)
@@ -1786,9 +1876,17 @@ class OrderCreateSerializer(I18nAwareModelSerializer):
                     else:
                         f.save()
             else:
-                f = OrderFee(**fee_data)
+                f = OrderFee(**{k: v for k, v in fee_data.items() if k not in (
+                    'tax_value',
+                    'value_includes_rounding_correction',
+                    'tax_value_includes_rounding_correction'
+                )})
                 f.order = order._wrapped if simulate else order
-                f._calculate_tax()
+                f._calculate_tax(
+                    override_tax_rate=fee_data.get('tax_rate'),
+                    override_tax_code=fee_data.get('tax_code'),
+                )
+                fee_data['__instance'] = f
                 fees.append(f)
                 if simulate:
                     f.id = 0
@@ -1820,7 +1918,47 @@ class OrderCreateSerializer(I18nAwareModelSerializer):
                     "value", "value_includes_rounding_correction", "tax_value", "tax_value_includes_rounding_correction"
                 ])
 
+        for i, pos_data in enumerate(positions_data):
+            pos = pos_data['__instance']
+            if 'tax_value' in pos_data and pos_data['tax_value'] != pos.tax_value:
+                raise ValidationError(f'Tax value {pos_data["tax_value"]} in position {pos.positionid} does not match backend computation of {pos.tax_value}.')
+            if 'price_includes_rounding_correction' in pos_data and pos_data['price_includes_rounding_correction'] != pos.price_includes_rounding_correction:
+                raise ValidationError(
+                    f'Price rounding {pos_data["price_includes_rounding_correction"]} in position {pos.positionid} does not '
+                    f'match backend computation of {pos.price_includes_rounding_correction}.'
+                )
+            if ('tax_value_includes_rounding_correction' in pos_data and
+                    pos_data['tax_value_includes_rounding_correction'] != pos.tax_value_includes_rounding_correction):
+                raise ValidationError(
+                    f'Tax rounding {pos_data["tax_value_includes_rounding_correction"]} in position {pos.positionid} does not '
+                    f'match backend computation of {pos.tax_value_includes_rounding_correction}.'
+                )
+
+        for i, fee_data in enumerate(fees_data):
+            if '__instance' not in fee_data:  # split fee not supported for this, validated in OrderFeeCreateSerializer
+                continue
+            fee = fee_data['__instance']
+            if 'tax_value' in fee_data and fee_data['tax_value'] != fee.tax_value:
+                raise ValidationError(f'Tax value {fee_data["tax_value"]} in fee does not match backend computation of {fee.tax_value}.')
+            if 'value_includes_rounding_correction' in fee_data and fee_data['value_includes_rounding_correction'] != fee.value_includes_rounding_correction:
+                raise ValidationError(
+                    f'Price rounding {fee_data["value_includes_rounding_correction"]} in fee does not '
+                    f'match backend computation of {fee.value_includes_rounding_correction}.'
+                )
+            if ('tax_value_includes_rounding_correction' in fee_data and
+                    fee_data['tax_value_includes_rounding_correction'] != fee.tax_value_includes_rounding_correction):
+                raise ValidationError(
+                    f'Tax rounding {fee_data["tax_value_includes_rounding_correction"]} in fee does not '
+                    f'match backend computation of {fee.tax_value_includes_rounding_correction}.'
+                )
+
         order.total = sum([c.price for c in pos_map.values()]) + sum([f.value for f in fees])
+
+        if expected_total is not None and expected_total != order.total:
+            raise ValidationError({
+                'total': [f'Order total of {expected_total} does not match backend computation of {order.total}.']
+            })
+
         if simulate:
             order.fees = fees
             order.positions = pos_map.values()

src/pretix/base/models/orders.py

@@ -2450,7 +2450,7 @@ class OrderFee(RoundingCorrectionMixin, models.Model):
             self.fee_type, self.value
         )
 
-    def _calculate_tax(self, tax_rule=None, invoice_address=None, event=None):
+    def _calculate_tax(self, tax_rule=None, invoice_address=None, event=None, override_tax_rate=None, override_tax_code=None):
         if tax_rule:
             self.tax_rule = tax_rule
 
@@ -2469,7 +2469,8 @@ class OrderFee(RoundingCorrectionMixin, models.Model):
             self.tax_rule = event.cached_default_tax_rule
 
         if self.tax_rule:
-            tax = self.tax_rule.tax(self.value, base_price_is='gross', invoice_address=ia, force_fixed_gross_price=True)
+            tax = self.tax_rule.tax(self.value, base_price_is='gross', invoice_address=ia, force_fixed_gross_price=True,
+                                    override_tax_rate=override_tax_rate, override_tax_code=override_tax_code)
             self.tax_rate = tax.rate
             self.tax_code = tax.code
             self.tax_value = tax.tax
@@ -2832,14 +2833,15 @@ class OrderPosition(AbstractPosition):
             self.item.id, self.variation.id if self.variation else 0, self.order_id
         )
 
-    def _calculate_tax(self, tax_rule=None, invoice_address=None):
+    def _calculate_tax(self, tax_rule=None, invoice_address=None, override_tax_rate=None, override_tax_code=None):
         self.tax_rule = tax_rule or self.item.tax_rule
         try:
             ia = invoice_address or self.order.invoice_address
         except InvoiceAddress.DoesNotExist:
             ia = None
         if self.tax_rule:
-            tax = self.tax_rule.tax(self.price, invoice_address=ia, base_price_is='gross', force_fixed_gross_price=True)
+            tax = self.tax_rule.tax(self.price, invoice_address=ia, base_price_is='gross', force_fixed_gross_price=True,
+                                    override_tax_rate=override_tax_rate, override_tax_code=override_tax_code)
             self.tax_rate = tax.rate
             self.tax_code = tax.code
             self.tax_value = tax.tax

src/pretix/base/plugins.py

@@ -22,9 +22,9 @@
 import os
 import sys
 from enum import Enum
-from importlib import metadata
 from typing import List
 
+import importlib_metadata as metadata
 from django.apps import AppConfig, apps
 from django.conf import settings
 from django.core.exceptions import ImproperlyConfigured

src/pretix/base/templatetags/vite.py

@@ -23,10 +23,10 @@ import json
 import logging
 import pathlib
 import re
-from importlib import metadata
 from urllib.parse import urljoin
 from urllib.request import urlopen
 
+import importlib_metadata as metadata
 from django import template
 from django.conf import settings
 from django.utils.safestring import mark_safe

src/pretix/control/views/global_settings.py

@@ -31,8 +31,7 @@
 # Unless required by applicable law or agreed to in writing, software distributed under the Apache License 2.0 is
 # distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 # License for the specific language governing permissions and limitations under the License.
-from importlib import metadata as metadata
-
+import importlib_metadata as metadata
 from django.conf import settings
 from django.contrib import messages
 from django.db import transaction

src/pretix/settings.py

@@ -41,7 +41,7 @@ from json import loads
 from pathlib import Path
 from urllib.parse import urlparse
 
-from importlib import metadata
+import importlib_metadata as metadata
 from django.core.exceptions import ImproperlyConfigured
 from django.utils.crypto import get_random_string
 from kombu import Queue

src/tests/api/test_order_create.py

@@ -1012,6 +1012,58 @@ def test_order_create_tax_rules(token_client, organizer, event, item, quota, que
     assert pos.tax_rule == taxrule
 
 
+@pytest.mark.django_db
+def test_order_create_tax_rule_explicit(token_client, organizer, event, item, quota, question, taxrule):
+    item.tax_rule = None
+    item.save()
+    res = copy.deepcopy(ORDER_CREATE_PAYLOAD)
+    res['fees'][0]['tax_rule'] = taxrule.pk
+    res['positions'][0]['item'] = item.pk
+    res['positions'][0]['tax_rule'] = taxrule.pk
+    res['positions'][0]['answers'][0]['question'] = question.pk
+    resp = token_client.post(
+        '/api/v1/organizers/{}/events/{}/orders/'.format(
+            organizer.slug, event.slug
+        ), format='json', data=res
+    )
+    assert resp.status_code == 201
+    with scopes_disabled():
+        o = Order.objects.get(code=resp.data['code'])
+        pos = o.positions.first()
+    assert pos.item == item
+    assert pos.tax_rate == Decimal('19.00')
+    assert pos.tax_value == Decimal('3.67')
+    assert pos.tax_rule == taxrule
+    assert pos.tax_code == "S/standard"
+
+
+@pytest.mark.django_db
+def test_order_create_tax_rule_custom_rate_and_code(token_client, organizer, event, item, quota, question, taxrule):
+    item.tax_rule = None
+    item.save()
+    res = copy.deepcopy(ORDER_CREATE_PAYLOAD)
+    res['fees'][0]['tax_rule'] = taxrule.pk
+    res['positions'][0]['item'] = item.pk
+    res['positions'][0]['tax_rule'] = taxrule.pk
+    res['positions'][0]['tax_code'] = 'S/reduced'
+    res['positions'][0]['tax_rate'] = "7.00"
+    res['positions'][0]['answers'][0]['question'] = question.pk
+    resp = token_client.post(
+        '/api/v1/organizers/{}/events/{}/orders/'.format(
+            organizer.slug, event.slug
+        ), format='json', data=res
+    )
+    assert resp.status_code == 201
+    with scopes_disabled():
+        o = Order.objects.get(code=resp.data['code'])
+        pos = o.positions.first()
+    assert pos.item == item
+    assert pos.tax_rate == Decimal('7.00')
+    assert pos.tax_value == Decimal('1.50')
+    assert pos.tax_rule == taxrule
+    assert pos.tax_code == "S/reduced"
+
+
 @pytest.mark.django_db
 def test_order_create_fee_type_validation(token_client, organizer, event, item, quota, question):
     res = copy.deepcopy(ORDER_CREATE_PAYLOAD)
@@ -1107,6 +1159,75 @@ def test_order_create_fee_with_auto_tax(token_client, organizer, event, item, qu
         assert o.total == Decimal('25.30')
 
 
+@pytest.mark.django_db
+def test_order_create_fee_with_explicit_tax_and_percentage(token_client, organizer, event, item, quota, question, taxrule):
+    res = copy.deepcopy(ORDER_CREATE_PAYLOAD)
+    res['fees'][0]['tax_rate'] = '7.00'
+    res['fees'][0]['tax_rule'] = taxrule.pk
+    res['fees'][0]['_split_taxes_like_products'] = False
+    res['fees'][0]['_treat_value_as_percentage'] = True
+    res['fees'][0]['value'] = '10.00'
+    res['positions'][0]['item'] = item.pk
+    res['positions'][0]['answers'][0]['question'] = question.pk
+    item.tax_rule = taxrule
+    item.save()
+    resp = token_client.post(
+        '/api/v1/organizers/{}/events/{}/orders/'.format(
+            organizer.slug, event.slug
+        ), format='json', data=res
+    )
+    assert resp.status_code == 201
+    with scopes_disabled():
+        o = Order.objects.get(code=resp.data['code'])
+        fee = o.fees.first()
+        assert fee.value == Decimal('2.30')
+        assert fee.tax_rate == Decimal('7.00')
+        assert fee.tax_value == Decimal('0.15')
+        assert o.total == Decimal('25.30')
+
+
+@pytest.mark.django_db
+def test_order_create_fee_with_explicit_tax_and_split_requested(token_client, organizer, event, item, quota, question, taxrule):
+    res = copy.deepcopy(ORDER_CREATE_PAYLOAD)
+    res['fees'][0]['tax_rate'] = '7.00'
+    res['fees'][0]['tax_rule'] = taxrule.pk
+    res['fees'][0]['_split_taxes_like_products'] = True
+    res['fees'][0]['_treat_value_as_percentage'] = True
+    res['fees'][0]['value'] = '10.00'
+    res['positions'][0]['item'] = item.pk
+    res['positions'][0]['answers'][0]['question'] = question.pk
+    item.tax_rule = taxrule
+    item.save()
+    resp = token_client.post(
+        '/api/v1/organizers/{}/events/{}/orders/'.format(
+            organizer.slug, event.slug
+        ), format='json', data=res
+    )
+    assert resp.status_code == 400
+    assert resp.data == {
+        'fees': [{'tax_rate': ['You cannot ask for the value to be distributed over tax rates if you already set the tax rate or computed taxes.']}],
+    }
+
+    res['fees'][0]['tax_rate'] = '7.00'
+    res['fees'][0]['tax_value'] = '1.50'
+    res['fees'][0]['tax_rule'] = taxrule.pk
+    res['fees'][0]['_treat_value_as_percentage'] = True
+    res['fees'][0]['value'] = '10.00'
+    res['positions'][0]['item'] = item.pk
+    res['positions'][0]['answers'][0]['question'] = question.pk
+    item.tax_rule = taxrule
+    item.save()
+    resp = token_client.post(
+        '/api/v1/organizers/{}/events/{}/orders/'.format(
+            organizer.slug, event.slug
+        ), format='json', data=res
+    )
+    assert resp.status_code == 400
+    assert resp.data == {
+        'fees': [{'tax_value': ['You cannot ask for the value to be treated as a percentage if you already computed taxes.']}],
+    }
+
+
 @pytest.mark.django_db
 def test_order_create_negative_fee_with_auto_tax(token_client, organizer, event, item, quota, question, taxrule):
     res = copy.deepcopy(ORDER_CREATE_PAYLOAD)
@@ -1136,6 +1257,7 @@ def test_order_create_tax_rule_wrong_event(token_client, organizer, event, item,
     res = copy.deepcopy(ORDER_CREATE_PAYLOAD)
     res['fees'][0]['tax_rule'] = taxrule2.pk
     res['positions'][0]['item'] = item.pk
+    res['positions'][0]['tax_rule'] = taxrule2.pk
     res['positions'][0]['answers'][0]['question'] = question.pk
     resp = token_client.post(
         '/api/v1/organizers/{}/events/{}/orders/'.format(
@@ -1143,7 +1265,10 @@ def test_order_create_tax_rule_wrong_event(token_client, organizer, event, item,
         ), format='json', data=res
     )
     assert resp.status_code == 400
-    assert resp.data == {'fees': [{'tax_rule': ['The specified tax rate does not belong to this event.']}]}
+    assert resp.data == {
+        'positions': [{'tax_rule': ['The specified tax rule does not belong to this event.']}],
+        'fees': [{'tax_rule': ['The specified tax rule does not belong to this event.']}],
+    }
 
 
 @pytest.mark.django_db
@@ -3693,3 +3818,119 @@ def test_order_create_use_gift_card_invalid_secret(token_client, organizer, even
         assert o.payments.count() == 2
         assert o.payments.all()[0].state == OrderPayment.PAYMENT_STATE_FAILED
         assert o.payments.all()[1].state == OrderPayment.PAYMENT_STATE_CONFIRMED
+
+
+@pytest.mark.django_db
+@pytest.mark.parametrize("rounding_mode,data,error", [
+    ("line", {"tax_value": "2.40"}, "Tax value 2.40 in position 1 does not match backend computation of 2.39."),
+    ("line", {"tax_value": "2.39"}, None),
+    ("line", {"price_includes_rounding_correction": "0.01"}, "Price rounding 0.01 in position 1 does not match backend computation of 0.00."),
+    ("line", {"tax_value_includes_rounding_correction": "0.01"}, "Tax rounding 0.01 in position 1 does not match backend computation of 0.00."),
+    ("sum_by_net",
+     {"tax_value": "2.39"},
+     "Tax value 2.39 in position 1 does not match backend computation of 2.40."),
+    ("sum_by_net",
+     {"tax_value": "2.40", "price": "15.01", "price_includes_rounding_correction": "0.01"},
+     None),
+    ("sum_by_net",
+     {"tax_value": "2.40", "price": "15.00", "price_includes_rounding_correction": "0.00"},
+     "Price rounding 0.00 in position 1 does not match backend computation of 0.01."),
+    ("sum_by_net",
+     {"tax_value": "2.40", "price": "15.01", "price_includes_rounding_correction": "0.01", "tax_value_includes_rounding_correction": "0.00"},
+     "Tax rounding 0.00 in position 1 does not match backend computation of 0.01."),
+])
+def test_order_tax_match_validation(token_client, organizer, event, item, quota, question, taxrule,
+                                    rounding_mode, data, error):
+    res = copy.deepcopy(ORDER_CREATE_PAYLOAD)
+    del res['fees']
+    res['tax_rounding_mode'] = rounding_mode
+    res['positions'][0]['item'] = item.pk
+    res['positions'][0]['price'] = "15.00"
+    res['positions'][0]['tax_rule'] = taxrule.pk
+    res['positions'][0]['answers'][0]['question'] = question.pk
+    res['positions'][0].update(data)
+    resp = token_client.post(
+        '/api/v1/organizers/{}/events/{}/orders/'.format(
+            organizer.slug, event.slug
+        ), format='json', data=res
+    )
+    if error:
+        assert resp.status_code == 400
+        assert resp.data == [error]
+    else:
+        assert resp.status_code == 201
+
+
+@pytest.mark.django_db
+@pytest.mark.parametrize("rounding_mode,data,error", [
+    ("line", {"tax_value": "1.61"}, "Tax value 1.61 in fee does not match backend computation of 1.60."),
+    ("line", {"tax_value": "1.60"}, None),
+    ("line", {"value_includes_rounding_correction": "0.01"},
+     "Price rounding 0.01 in fee does not match backend computation of 0.00."),
+    ("line", {"tax_value_includes_rounding_correction": "0.01"},
+     "Tax rounding 0.01 in fee does not match backend computation of 0.00."),
+    ("sum_by_net",
+     {"tax_value": "1.60"},
+     "Tax value 1.60 in fee does not match backend computation of 1.59."),
+    ("sum_by_net",
+     {"tax_value": "1.59", "value": "9.99", "value_includes_rounding_correction": "-0.01"},
+     None),
+    ("sum_by_net",
+     {"tax_value": "1.59", "value": "10.00", "value_includes_rounding_correction": "0.00"},
+     "Price rounding 0.00 in fee does not match backend computation of -0.01."),
+    ("sum_by_net",
+     {"tax_value": "1.59", "value": "9.99", "value_includes_rounding_correction": "-0.01",
+      "tax_value_includes_rounding_correction": "0.00"},
+     "Tax rounding 0.00 in fee does not match backend computation of -0.01."),
+])
+def test_order_tax_match_validation_of_fee(token_client, organizer, event, item, quota, question, taxrule,
+                                           rounding_mode, data, error):
+    res = copy.deepcopy(ORDER_CREATE_PAYLOAD)
+    res['tax_rounding_mode'] = rounding_mode
+    res['positions'][0]['item'] = item.pk
+    res['positions'][0]['price'] = "5.00"
+    res['positions'][0]['tax_rule'] = taxrule.pk
+    res['positions'][0]['answers'][0]['question'] = question.pk
+    res['fees'][0]['value'] = "10.00"
+    res['fees'][0]['tax_rule'] = taxrule.pk
+    res['fees'][0].update(data)
+    resp = token_client.post(
+        '/api/v1/organizers/{}/events/{}/orders/'.format(
+            organizer.slug, event.slug
+        ), format='json', data=res
+    )
+    if error:
+        assert resp.status_code == 400
+        assert resp.data == [error]
+    else:
+        assert resp.status_code == 201
+
+
+@pytest.mark.django_db
+def test_order_expect_total(token_client, organizer, event, item, quota, question, taxrule):
+    # Force a rounding difference to make sure it's the last step of total computation that is compared
+    res = copy.deepcopy(ORDER_CREATE_PAYLOAD)
+    del res['fees']
+    res['tax_rounding_mode'] = "sum_by_net"
+    res['positions'][0]['item'] = item.pk
+    res['positions'][0]['price'] = "15.00"
+    res['positions'][0]['tax_rule'] = taxrule.pk
+    res['positions'][0]['answers'][0]['question'] = question.pk
+    res['total'] = "15.00"
+    resp = token_client.post(
+        '/api/v1/organizers/{}/events/{}/orders/'.format(
+            organizer.slug, event.slug
+        ), format='json', data=res
+    )
+    assert resp.status_code == 400
+    assert resp.data == {
+        'total': ['Order total of 15.00 does not match backend computation of 15.01.']
+    }
+
+    res['total'] = "15.01"
+    resp = token_client.post(
+        '/api/v1/organizers/{}/events/{}/orders/'.format(
+            organizer.slug, event.slug
+        ), format='json', data=res
+    )
+    assert resp.status_code == 201