Add documentation

doc/api/resources/invoices.rst

@@ -80,17 +80,12 @@ lines                                 list of objects            The actual invo
                                                                  for all invoice lines
                                                                  created before this field was introduced as well as for
                                                                  all lines not created by a fee (e.g. a product).
-├ event_date_from                     datetime                   Start date of the (sub)event this line was created for as it
-                                                                 was set during invoice creation. Can be ``null`` for all invoice
-                                                                 lines created before this was introduced as well as for lines in
-                                                                 an event series not created by a product (e.g. shipping or
-                                                                 cancellation fees).
-├ event_date_to                       datetime                   End date of the (sub)event this line was created for as it
-                                                                 was set during invoice creation. Can be ``null`` for all invoice
-                                                                 lines created before this was introduced as well as for lines in
-                                                                 an event series not created by a product (e.g. shipping or
-                                                                 cancellation fees) as well as whenever the respective (sub)event
-                                                                 has no end date set.
+├ period_start                        datetime                   Start date of the service or delivery period of the invoice line.
+                                                                 Can be ``null`` if not known.
+├ period_end                        datetime                     End date of the service or delivery period of the invoice line.
+                                                                 Can be ``null`` if not known.
+├ event_date_from                     datetime                   Deprecated alias of ``period_start``.
+├ event_date_to                       datetime                   Deprecated alias of ``period_end``.
 ├ event_location                      string                     Location of the (sub)event this line was created for as it
                                                                  was set during invoice creation. Can be ``null`` for all invoice
                                                                  lines created before this was introduced as well as for lines in
@@ -274,6 +269,8 @@ List of all invoices
                 "fee_internal_type": null,
                 "event_date_from": "2017-12-27T10:00:00Z",
                 "event_date_to": null,
+                "period_start": "2017-12-27T10:00:00Z",
+                "period_end": "2017-12-27T10:00:00Z",
                 "event_location": "Heidelberg",
                 "attendee_name": null,
                 "gross_value": "23.00",
@@ -420,6 +417,8 @@ Fetching individual invoices
             "fee_internal_type": null,
             "event_date_from": "2017-12-27T10:00:00Z",
             "event_date_to": null,
+            "period_start": "2017-12-27T10:00:00Z",
+            "period_end": "2017-12-27T10:00:00Z",
             "event_location": "Heidelberg",
             "attendee_name": null,
             "gross_value": "23.00",

doc/development/api/general.rst

@@ -23,7 +23,7 @@ There are multiple signals that will be sent out in the ordering cycle:
 
 .. automodule:: pretix.base.signals
    :no-index:
-   :members: validate_cart, validate_cart_addons, validate_order, order_valid_if_pending, order_fee_calculation, order_paid, order_placed, order_canceled, order_reactivated, order_expired, order_expiry_changed, order_modified, order_changed, order_approved, order_denied, order_fee_type_name, allow_ticket_download, order_split, order_gracefully_delete, invoice_line_text
+   :members: validate_cart, validate_cart_addons, validate_order, order_valid_if_pending, order_fee_calculation, order_paid, order_placed, order_canceled, order_reactivated, order_expired, order_expiry_changed, order_modified, order_changed, order_approved, order_denied, order_fee_type_name, allow_ticket_download, order_split, order_gracefully_delete, build_invoice_data, invoice_line_text
 
 Check-ins
 """""""""

src/pretix/api/serializers/event.py

@@ -805,6 +805,7 @@ class EventSettingsSerializer(SettingsSerializer):
         'invoice_reissue_after_modify',
         'invoice_include_free',
         'invoice_generate',
+        'invoice_period',
         'invoice_numbers_consecutive',
         'invoice_numbers_prefix',
         'invoice_numbers_prefix_cancellations',

src/pretix/api/serializers/order.py

@@ -1757,12 +1757,14 @@ class LinePositionField(serializers.IntegerField):
 
 class InlineInvoiceLineSerializer(I18nAwareModelSerializer):
     position = LinePositionField(read_only=True)
+    event_date_from = serializers.DateTimeField(read_only=True, source="period_start")
+    event_date_to = serializers.DateTimeField(read_only=True, source="period_end")
 
     class Meta:
         model = InvoiceLine
         fields = ('position', 'description', 'item', 'variation', 'subevent', 'attendee_name', 'event_date_from',
-                  'event_date_to', 'gross_value', 'tax_value', 'tax_rate', 'tax_code', 'tax_name', 'fee_type',
-                  'fee_internal_type', 'event_location')
+                  'event_date_to', 'period_start', 'period_end', 'gross_value', 'tax_value', 'tax_rate', 'tax_code',
+                  'tax_name', 'fee_type', 'fee_internal_type', 'event_location')
 
 
 class InvoiceSerializer(I18nAwareModelSerializer):

src/pretix/base/invoicing/pdf.py

@@ -19,6 +19,7 @@
 # You should have received a copy of the GNU Affero General Public License along with this program.  If not, see
 # <https://www.gnu.org/licenses/>.
 #
+import datetime
 import logging
 import re
 import unicodedata
@@ -522,6 +523,20 @@ class ClassicInvoiceRenderer(BaseReportlabInvoiceRenderer):
         textobject.textLine(self._normalize(self._upper(pgettext('invoice', 'Event'))))
         canvas.drawText(textobject)
 
+    def _date_range_in_header(self):
+        if self.invoice.event.has_subevents or not self.invoice.event.settings.show_dates_on_frontpage:
+            return None, None
+        tz = self.invoice.event.timezone
+        show_end_date = (
+            self.invoice.event.settings.show_date_to and
+            self.invoice.event.date_to and
+            self.invoice.event.date_to.astimezone(tz).date() != self.invoice.event.date_from.astimezone(tz).date()
+        )
+        if show_end_date:
+            return self.invoice.event.date_from.astimezone(tz).date(), self.invoice.event.date_to.astimezone(tz).date()
+        else:
+            return self.invoice.event.date_from.astimezone(tz).date(), None
+
     def _draw_event(self, canvas):
         def shorten(txt):
             txt = str(txt)
@@ -535,25 +550,17 @@ class ClassicInvoiceRenderer(BaseReportlabInvoiceRenderer):
                 p_size = p.wrap(self.event_width, self.event_height)
             return txt
 
-        if not self.invoice.event.has_subevents and self.invoice.event.settings.show_dates_on_frontpage:
-            tz = self.invoice.event.timezone
-            show_end_date = (
-                self.invoice.event.settings.show_date_to and
-                self.invoice.event.date_to and
-                self.invoice.event.date_to.astimezone(tz).date() != self.invoice.event.date_from.astimezone(tz).date()
+        d_from, d_to = self._date_range_in_header()
+        if d_from and d_to:
+            p_str = (
+                shorten(self.invoice.event.name) + '\n' +
+                pgettext('invoice', '{from_date}\nuntil {to_date}').format(
+                    from_date=date_format(d_from, "DATE_FORMAT"),
+                    to_date=date_format(d_to, "DATE_FORMAT"),
+                )
             )
-            if show_end_date:
-                p_str = (
-                    shorten(self.invoice.event.name) + '\n' +
-                    pgettext('invoice', '{from_date}\nuntil {to_date}').format(
-                        from_date=self.invoice.event.get_date_from_display(show_times=False),
-                        to_date=self.invoice.event.get_date_to_display(show_times=False)
-                    )
-                )
-            else:
-                p_str = (
-                    shorten(self.invoice.event.name) + '\n' + self.invoice.event.get_date_from_display(show_times=False)
-                )
+        elif d_from:
+            p_str = shorten(self.invoice.event.name) + '\n' + date_format(d_from, "DATE_FORMAT")
         else:
             p_str = shorten(self.invoice.event.name)
 
@@ -657,6 +664,12 @@ class ClassicInvoiceRenderer(BaseReportlabInvoiceRenderer):
 
     def _get_story(self, doc):
         has_taxes = any(il.tax_value for il in self.invoice.lines.all()) or self.invoice.reverse_charge
+        header_dates = self._date_range_in_header()
+        tz = self.invoice.event.timezone
+        has_multiple_service_dates = len(set(
+            (il.period_start, il.period_end) for il in self.invoice.lines.all()
+        )) > 1
+        request_show_service_date = False
 
         story = [
             NextPageTemplate('FirstPage'),
@@ -700,15 +713,73 @@ class ClassicInvoiceRenderer(BaseReportlabInvoiceRenderer):
             )]
 
         def _group_key(line):
-            return (line.description, line.tax_rate, line.tax_name, line.net_value, line.gross_value, line.subevent_id,
-                    line.event_date_from, line.event_date_to)
+            return (line.description, line.tax_rate, line.tax_name, line.net_value, line.gross_value, line.subevent,
+                    line.period_start, line.period_end)
+
+        def day(dt: datetime.datetime) -> datetime.date:
+            if dt is None:
+                return None
+            return dt.astimezone(tz).date()
 
         total = Decimal('0.00')
-        for (description, tax_rate, tax_name, net_value, gross_value, *ignored), lines in addon_aware_groupby(
+        for (description, tax_rate, tax_name, net_value, gross_value, subevent, period_start, period_end), lines in addon_aware_groupby(
             self.invoice.lines.all(),
             key=_group_key,
             is_addon=lambda l: l.description.startswith("  +"),
         ):
+            # Try to be clever and figure out when organizers would want to show the period. This heuristic is
+            # not perfect and the only "fully correct" way would be to include the period on every line always,
+            # however this will cause confusion (a) due to useless repetition of the same date all over the invoice
+            # (b) due to not respecting the show_date_to setting of events in cases where we could have respected it.
+            # Still, we want to show the date explicitly if its different to the event or invoice date.
+            if period_start and period_end and day(period_end) != day(period_start):
+                # It's a multi-day period, such as the validity of the ticket or an event date period
+
+                if day(period_start) == header_dates[0] and day(period_end) == header_dates[1]:
+                    # This is the exact event period we already printed in the header, no need to repeat it.
+                    period_line = ""
+
+                elif (self.event.has_subevents and subevent and day(subevent.date_from) == day(period_start) and
+                      day(subevent.date_to) == day(period_end)):
+                    # For subevents, build_invoice already includes the date in the description in the event-default format.
+                    period_line = ""
+
+                else:
+                    period_line = f"{date_format(day(period_start), 'SHORT_DATE_FORMAT')} – {date_format(day(period_end), 'SHORT_DATE_FORMAT')}"
+
+            elif period_start or period_end:
+                # It's a single-day period
+
+                delivery_day = day(period_end or period_start)
+                if delivery_day in (header_dates[0], header_dates[1]):
+                    # This is the event date we already printed in the header, no need to repeat it.
+                    period_line = ""
+
+                elif self.event.has_subevents and subevent and delivery_day in (day(subevent.date_from), day(subevent.date_to)):
+                    # For subevents, build_invoice already includes the date in the description in the event-default format.
+                    period_line = ""
+
+                elif (delivery_day == self.invoice.date) and header_dates[0] is None:
+                    # This is a shop that doesn't show the date of the event in the header, and the period is the invoice
+                    # date. We assume that this is an 'everything is executed immediately' situation and do not want to
+                    # confuse with showing additional dates on the invoice. This is the case that is not guaranteed to be
+                    # correct in all cases and might need to change in the future. If customers have legal concerns, a
+                    # quick fix is including a sentence like "Delivery date is the invoice date unless otherwise indicated:"
+                    # in a custom text on the invoice.
+                    period_line = ""
+
+                else:
+                    period_line = date_format(delivery_day, 'SHORT_DATE_FORMAT')
+            else:
+                # No period known
+                period_line = ""
+
+            if not has_multiple_service_dates and period_line:
+                # Group together at the end of the invoice
+                request_show_service_date = period_line
+            else:
+                description += "\n" + period_line
+
             lines = list(lines)
             if has_taxes:
                 if len(lines) > 1:
@@ -717,6 +788,7 @@ class ClassicInvoiceRenderer(BaseReportlabInvoiceRenderer):
                         gross_price=money_filter(gross_value, self.invoice.event.currency),
                     )
                     description = description + "\n" + single_price_line
+
                 tdata.append((
                     FontFallbackParagraph(
                         self._clean_text(description, tags=['br']),
@@ -821,6 +893,12 @@ class ClassicInvoiceRenderer(BaseReportlabInvoiceRenderer):
 
         story.append(Spacer(1, 10 * mm))
 
+        if request_show_service_date:
+            story.append(FontFallbackParagraph(
+                self._normalize(pgettext('invoice', 'Invoice period: {daterange}').format(daterange=request_show_service_date)),
+                self.stylesheet['Normal']
+            ))
+
         if self.invoice.payment_provider_text:
             story.append(FontFallbackParagraph(
                 self._normalize(self.invoice.payment_provider_text),

src/pretix/base/migrations/0289_invoiceline_period.py

@@ -0,0 +1,80 @@
+# Generated by Django 4.2.17 on 2025-09-08 08:14
+from django.core.cache import cache
+from django.db import migrations
+
+
+def set_invoice_period(apps, schema_editor):
+    EventSettingsStore = apps.get_model("pretixbase", "Event_SettingsStore")
+    ev_seen = set()
+    insert_queue = []
+    flush_queue = []
+
+    def store():
+        EventSettingsStore.objects.bulk_create(
+            insert_queue,
+            update_conflicts=True,
+            update_fields=["value"],
+            unique_fields=["object", "key"],
+        )
+        for f in flush_queue:
+            cache.delete(f)
+        flush_queue.clear()
+        insert_queue.clear()
+
+    # Existing events that use pretix-zugferd and have explicitly disabled delivery dates
+    for setting in EventSettingsStore.objects.filter(key="zugferd_include_delivery_date", value="False"):
+        flush_queue.append("hierarkey_{}_{}".format("event", setting.object_id))
+        insert_queue.append(
+            EventSettingsStore(
+                object_id=setting.object_id,
+                key="invoice_period",
+                value="invoice_date",
+            )
+        )
+        ev_seen.add(setting.object_id)
+
+        if len(insert_queue) > 1000:
+            store()
+
+    # Existing events that previously hid their date on invoices
+    for setting in EventSettingsStore.objects.filter(key="show_dates_on_frontpage", value="False"):
+        if setting.object_id in ev_seen:
+            continue
+
+        flush_queue.append("hierarkey_{}_{}".format("event", setting.object_id))
+        insert_queue.append(
+            EventSettingsStore(
+                object_id=setting.object_id,
+                key="invoice_period",
+                value="auto_no_event",
+            )
+        )
+        ev_seen.add(setting.object_id)
+
+        if len(insert_queue) > 1000:
+            store()
+
+    store()
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("pretixbase", "0288_invoice_transmission"),
+    ]
+
+    operations = [
+        migrations.RenameField(
+            model_name="invoiceline",
+            old_name="event_date_to",
+            new_name="period_end",
+        ),
+        migrations.RenameField(
+            model_name="invoiceline",
+            old_name="event_date_from",
+            new_name="period_start",
+        ),
+        migrations.RunPython(
+            set_invoice_period,
+            migrations.RunPython.noop,
+        )
+    ]

src/pretix/base/migrations/0290_invoice_plugin_data.py

@@ -0,0 +1,18 @@
+# Generated by Django 4.2.17 on 2025-09-09 09:55
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("pretixbase", "0289_invoiceline_period"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="invoice",
+            name="plugin_data",
+            field=models.JSONField(default=dict),
+        ),
+    ]

src/pretix/base/models/invoices.py

@@ -33,6 +33,7 @@
 # License for the specific language governing permissions and limitations under the License.
 
 import string
+import warnings
 from decimal import Decimal
 
 import pycountry
@@ -200,6 +201,7 @@ class Invoice(models.Model):
     transmission_info = models.JSONField(null=True, blank=True)
 
     file = models.FileField(null=True, blank=True, upload_to=invoice_filename, max_length=255)
+    plugin_data = models.JSONField(default=dict)
 
     objects = ScopedManager(organizer='event__organizer')
 
@@ -387,10 +389,10 @@ class InvoiceLine(models.Model):
     :type tax_name: str
     :param subevent: The subevent this line refers to
     :type subevent: SubEvent
-    :param event_date_from: Event date of the (sub)event at the time the invoice was created
-    :type event_date_from: datetime
-    :param event_date_to: Event end date of the (sub)event at the time the invoice was created
-    :type event_date_to: datetime
+    :param period_start: Start if service period invoiced
+    :type period_start: datetime
+    :param period_end: End of service period invoiced
+    :type period_end: datetime
     :param event_location: Event location of the (sub)event at the time the invoice was created
     :type event_location: str
     :param item: The item this line refers to
@@ -409,8 +411,8 @@ class InvoiceLine(models.Model):
     tax_name = models.CharField(max_length=190)
     tax_code = models.CharField(max_length=190, null=True, blank=True)
     subevent = models.ForeignKey('SubEvent', null=True, blank=True, on_delete=models.PROTECT)
-    event_date_from = models.DateTimeField(null=True)
-    event_date_to = models.DateTimeField(null=True)
+    period_start = models.DateTimeField(null=True)
+    period_end = models.DateTimeField(null=True)
     event_location = models.TextField(null=True, blank=True)
     item = models.ForeignKey('Item', null=True, blank=True, on_delete=models.PROTECT)
     variation = models.ForeignKey('ItemVariation', null=True, blank=True, on_delete=models.PROTECT)
@@ -427,3 +429,35 @@ class InvoiceLine(models.Model):
 
     def __str__(self):
         return 'Line {} of invoice {}'.format(self.position, self.invoice)
+
+    @property
+    def event_date_from(self):
+        warnings.warn(
+            'InvoiceLine.event_date_from is deprecated, use period_start instead,',
+            category=DeprecationWarning,
+        )
+        return self.period_start
+
+    @event_date_from.setter
+    def event_date_from(self, value):
+        warnings.warn(
+            'InvoiceLine.event_date_from is deprecated, use period_start instead,',
+            category=DeprecationWarning,
+        )
+        self.period_start = value
+
+    @property
+    def event_date_to(self):
+        warnings.warn(
+            'InvoiceLine.event_date_to is deprecated, use period_end instead,',
+            category=DeprecationWarning,
+        )
+        return self.period_end
+
+    @event_date_to.setter
+    def event_date_to(self, value):
+        warnings.warn(
+            'InvoiceLine.event_date_to is deprecated, use period_end instead,',
+            category=DeprecationWarning,
+        )
+        self.period_to = value

src/pretix/base/services/invoices.py

@@ -61,7 +61,9 @@ from pretix.base.models.tax import EU_CURRENCIES
 from pretix.base.services.tasks import (
     TransactionAwareProfiledEventTask, TransactionAwareTask,
 )
-from pretix.base.signals import invoice_line_text, periodic_task
+from pretix.base.signals import (
+    build_invoice_data, invoice_line_text, periodic_task,
+)
 from pretix.celery_app import app
 from pretix.helpers.database import OF_SELF, rolledback_transaction
 from pretix.helpers.models import modelcopy
@@ -82,6 +84,10 @@ def build_invoice(invoice: Invoice) -> Invoice:
 
     lp = invoice.order.payments.last()
 
+    min_period_start = None
+    max_period_end = None
+    now_dt = now()
+
     with (language(invoice.locale, invoice.event.settings.region)):
         invoice.invoice_from = invoice.event.settings.get('invoice_address_from')
         invoice.invoice_from_name = invoice.event.settings.get('invoice_address_from_name')
@@ -208,7 +214,9 @@ def build_invoice(invoice: Invoice) -> Invoice:
         positions = list(
             invoice.order.positions.select_related('addon_to', 'item', 'tax_rule', 'subevent', 'variation').annotate(
                 addon_c=Count('addons')
-            ).prefetch_related('answers', 'answers__options', 'answers__question').order_by('positionid', 'id')
+            ).prefetch_related(
+                'answers', 'answers__options', 'answers__question', 'granted_memberships',
+            ).order_by('positionid', 'id')
         )
 
         reverse_charge = False
@@ -267,6 +275,10 @@ def build_invoice(invoice: Invoice) -> Invoice:
                     location=_location_oneliner(location)
                 )
 
+            period_start, period_end = _service_period_for_position(invoice, p, now_dt)
+            min_period_start = min(min_period_start or period_start, period_start)
+            max_period_end = min(max_period_end or period_end, period_end)
+
             InvoiceLine.objects.create(
                 position=i,
                 invoice=invoice,
@@ -277,8 +289,8 @@ def build_invoice(invoice: Invoice) -> Invoice:
                 item=p.item,
                 variation=p.variation,
                 attendee_name=p.attendee_name if invoice.event.settings.invoice_attendee_name else None,
-                event_date_from=p.subevent.date_from if invoice.event.has_subevents else invoice.event.date_from,
-                event_date_to=p.subevent.date_to if invoice.event.has_subevents else invoice.event.date_to,
+                period_start=period_start,
+                period_end=period_end,
                 event_location=location if invoice.event.settings.invoice_event_location else None,
                 tax_rate=p.tax_rate,
                 tax_code=p.tax_code,
@@ -301,13 +313,29 @@ def build_invoice(invoice: Invoice) -> Invoice:
                 fee_title = _(fee.get_fee_type_display())
                 if fee.description:
                     fee_title += " - " + fee.description
+
+            if min_period_start and max_period_end:
+                # Consider fees to have the same service period as the products sold
+                period_start = min_period_start
+                period_end = max_period_end
+            else:
+                # Usually can only happen if everything except a cancellation fee is removed
+                if invoice.event.settings.invoice_period in ("auto", "auto_no_event", "event_date") and not invoice.event.has_subevents:
+                    # Non-series event, let's be backwards-compatible and tag everything with the event period
+                    period_start = invoice.event.date_from
+                    period_end = invoice.event.date_to
+                else:
+                    # We could try to work from the canceled positions, but it doesn't really make sense. A cancellation
+                    # fee is not "delivered" at the event date, it is rather effective right now.
+                    period_start = period_end = now()
+
             InvoiceLine.objects.create(
                 position=i + offset,
                 invoice=invoice,
                 description=fee_title,
                 gross_value=fee.value,
-                event_date_from=None if invoice.event.has_subevents else invoice.event.date_from,
-                event_date_to=None if invoice.event.has_subevents else invoice.event.date_to,
+                period_start=period_start,
+                period_end=period_end,
                 event_location=(
                     None if invoice.event.has_subevents
                     else (str(invoice.event.location)
@@ -336,6 +364,7 @@ def build_invoice(invoice: Invoice) -> Invoice:
         invoice.reverse_charge = reverse_charge
         invoice.save()
 
+        build_invoice_data.send(sender=invoice.event, invoice=invoice)
         return invoice
 
 
@@ -351,6 +380,49 @@ def build_cancellation(invoice: Invoice):
     return invoice
 
 
+def _service_period_for_position(invoice, position, invoice_dt):
+    if invoice.event.settings.invoice_period in ("auto", "auto_no_event"):
+        if position.valid_from or position.valid_until:
+            period_start = position.valid_from or now()
+            period_end = position.valid_until
+        elif memberships := list(position.granted_memberships.all()):
+            period_start = min(m.date_start for m in memberships)
+            period_end = max(m.date_end for m in memberships)
+        elif invoice.event.has_subevents:
+            if position.subevent:
+                period_start = position.subevent.date_from
+                period_end = position.subevent.date_to
+            else:
+                # Currently impossible case, but might not be in the future and never makes
+                # sense to use the event date here
+                period_start = invoice_dt
+                period_end = invoice_dt
+        elif invoice.event.settings.invoice_period == "auto_no_event":
+            period_start = invoice_dt
+            period_end = invoice_dt
+        else:
+            period_start = invoice.event.date_from
+            period_end = invoice.event.date_to
+    elif invoice.event.settings.invoice_period == "order_date":
+        period_start = invoice.order.datetime
+        period_end = invoice.order.datetime
+    elif invoice.event.settings.invoice_period == "event_date":
+        if position.subevent:
+            period_start = position.subevent.date_from
+            period_end = position.subevent.date_to
+        else:
+            period_start = invoice.event.date_from
+            period_end = invoice.event.date_to
+    elif invoice.event.settings.invoice_period == "invoice_date":
+        period_start = period_end = invoice_dt
+    else:
+        raise ValueError(f"Invalid invoice period setting '{invoice.event.settings.invoice_period}'")
+
+    if not period_end:
+        period_end = period_start
+    return period_start, period_end
+
+
 def generate_cancellation(invoice: Invoice, trigger_pdf=True):
     if invoice.canceled:
         raise ValueError("Invoice should not be canceled twice.")
@@ -456,6 +528,12 @@ def build_preview_invoice_pdf(event):
     if not locale or locale == '__user__':
         locale = event.settings.locale
 
+    if event.settings.invoice_period in ("auto", "auto_no_event", "event_date"):
+        period_start = event.date_from
+        period_end = event.date_to or event.date_from
+    else:
+        period_start = period_end = timezone.now()
+
     with rolledback_transaction(), language(locale, event.settings.region):
         order = event.orders.create(
             status=Order.STATUS_PENDING, datetime=timezone.now(),
@@ -506,8 +584,8 @@ def build_preview_invoice_pdf(event):
                         invoice=invoice, description=_("Sample product {}").format(i + 1),
                         gross_value=tax.gross, tax_value=tax.tax,
                         tax_rate=tax.rate, tax_name=tax.name, tax_code=tax.code,
-                        event_date_from=event.date_from,
-                        event_date_to=event.date_to,
+                        period_start=period_start,
+                        period_end=period_end,
                         event_location=event.settings.invoice_event_location,
                     )
         else:
@@ -515,8 +593,8 @@ def build_preview_invoice_pdf(event):
                 InvoiceLine.objects.create(
                     invoice=invoice, description=_("Sample product A"),
                     gross_value=100, tax_value=0, tax_rate=0, tax_code=None,
-                    event_date_from=event.date_from,
-                    event_date_to=event.date_to,
+                    period_start=period_start,
+                    period_end=period_end,
                     event_location=event.settings.invoice_event_location,
                 )
 

src/pretix/base/settings.py

@@ -1098,6 +1098,35 @@ DEFAULTS = {
             help_text=_("Invoices will never be automatically generated for free orders.")
         )
     },
+    'invoice_period': {
+        'default': 'auto',
+        'type': str,
+        'form_class': forms.ChoiceField,
+        'serializer_class': serializers.ChoiceField,
+        'serializer_kwargs': dict(
+            choices=(
+                ('auto', _('Automatic based on ticket-specific validity, membership validity, event series date, or event date)')),
+                ('auto_no_event', _('Automatic, but prefer invoice date over event date')),
+                ('event_date', _('Event date')),
+                ('order_date', _('Order date')),
+                ('invoice_date', _('Invoice date')),
+            ),
+        ),
+        'form_kwargs': dict(
+            label=_("Date of service"),
+            widget=forms.RadioSelect,
+            choices=(
+                ('auto', _('Automatic based on ticket-specific validity, membership validity, event series date, or event date)')),
+                ('auto_no_event', _('Automatic, but prefer invoice date over event date')),
+                ('event_date', _('Event date')),
+                ('order_date', _('Order date')),
+                ('invoice_date', _('Invoice date')),
+            ),
+            help_text=_("This controls what dates are shown on the invoice, but is especially important for "
+                        "electronic invoicing."),
+            required=True,
+        )
+    },
     'invoice_reissue_after_modify': {
         'default': 'False',
         'type': bool,

src/pretix/base/signals.py

@@ -596,6 +596,18 @@ multiple events. Receivers should return a subclass of pretix.base.exporter.Base
 The ``sender`` keyword argument will contain an organizer.
 """
 
+build_invoice_data = EventPluginSignal()
+"""
+Arguments: ``invoice``
+
+This signal is sent out every time an invoice is built, after the invoice model was created
+and filled and before the PDF generation task is started. You can use this to make changes
+to the invoice, but we recommend to mostly use it to add content to ``Invoice.plugin_data``.
+You are responsible for saving any changes to the database.
+
+As with all event-plugin signals, the ``sender`` keyword argument will contain the event.
+"""
+
 validate_order = EventPluginSignal()
 """
 Arguments: ``payments``, ``positions``, ``email``, ``locale``, ``invoice_address``,

src/pretix/control/forms/event.py

@@ -857,6 +857,7 @@ class InvoiceSettingsForm(EventSettingsValidationMixin, SettingsForm):
         'invoice_show_payments',
         'invoice_reissue_after_modify',
         'invoice_generate',
+        'invoice_period',
         'invoice_attendee_name',
         'invoice_event_location',
         'invoice_include_expire_date',

src/pretix/control/templates/pretixcontrol/event/invoicing.html

@@ -15,6 +15,19 @@
                 {% bootstrap_field form.invoice_email_attachment layout="control" %}
                 {% bootstrap_field form.invoice_email_organizer layout="control" %}
                 {% bootstrap_field form.invoice_language layout="control" %}
+                {% bootstrap_field form.invoice_period layout="control" %}
+
+                {% if not request.event.settings.show_dates_on_frontpage %}
+                    <div data-display-dependency="input[name=invoice_period][value=auto],input[name=invoice_period][value=event_date]">
+                        <div class="alert alert-warning dynamic">
+                            {% blocktrans trimmed %}
+                                You configured that your shop is not an event and the event date should not be shown.
+                                Therefore, we recommend that you set the date of service to a different option.
+                            {% endblocktrans %}
+                        </div>
+                    </div>
+                {% endif %}
+
                 {% bootstrap_field form.invoice_include_free layout="control" %}
                 {% bootstrap_field form.invoice_show_payments layout="control" %}
                 {% bootstrap_field form.invoice_reissue_after_modify layout="control" %}

src/tests/api/test_invoices.py

@@ -231,7 +231,9 @@ TEST_INVOICE_RES = {
             "description": "Budget Ticket<br />Attendee: Peter",
             'subevent': None,
             'event_date_from': '2017-12-27T10:00:00Z',
-            'event_date_to': None,
+            'event_date_to': '2017-12-27T10:00:00Z',
+            'period_start': '2017-12-27T10:00:00Z',
+            'period_end': '2017-12-27T10:00:00Z',
             'event_location': None,
             'attendee_name': 'Peter',
             'item': None,
@@ -249,7 +251,9 @@ TEST_INVOICE_RES = {
             "description": "Payment fee",
             'subevent': None,
             'event_date_from': '2017-12-27T10:00:00Z',
-            'event_date_to': None,
+            'event_date_to': '2017-12-27T10:00:00Z',
+            'period_start': '2017-12-27T10:00:00Z',
+            'period_end': '2017-12-27T10:00:00Z',
             'event_location': None,
             'attendee_name': None,
             'fee_type': "payment",

src/tests/api/test_order_change.py

@@ -608,7 +608,9 @@ def test_order_create_invoice(token_client, organizer, event, order):
                 'description': 'Budget Ticket<br />Attendee: Peter',
                 'subevent': None,
                 'event_date_from': '2017-12-27T10:00:00Z',
-                'event_date_to': None,
+                'event_date_to': '2017-12-27T10:00:00Z',
+                'period_start': '2017-12-27T10:00:00Z',
+                'period_end': '2017-12-27T10:00:00Z',
                 'event_location': None,
                 'fee_type': None,
                 'fee_internal_type': None,
@@ -626,7 +628,9 @@ def test_order_create_invoice(token_client, organizer, event, order):
                 'description': 'Payment fee',
                 'subevent': None,
                 'event_date_from': '2017-12-27T10:00:00Z',
-                'event_date_to': None,
+                'event_date_to': '2017-12-27T10:00:00Z',
+                'period_start': '2017-12-27T10:00:00Z',
+                'period_end': '2017-12-27T10:00:00Z',
                 'event_location': None,
                 'fee_type': "payment",
                 'fee_internal_type': None,

src/tests/base/test_invoices.py

@@ -33,7 +33,7 @@
 # License for the specific language governing permissions and limitations under the License.
 
 import json
-from datetime import date, timedelta
+from datetime import date, datetime, timedelta, timezone
 from decimal import Decimal
 
 import pytest
@@ -42,6 +42,7 @@ from django.utils.itercompat import is_iterable
 from django.utils.timezone import now
 from django_countries.fields import Country
 from django_scopes import scope, scopes_disabled
+from i18nfield.strings import LazyI18nString
 
 from pretix.base.invoice import addon_aware_groupby
 from pretix.base.models import (
@@ -62,7 +63,8 @@ def env():
     with scope(organizer=o):
         event = Event.objects.create(
             organizer=o, name='Dummy', slug='dummy',
-            date_from=now(), plugins='pretix.plugins.banktransfer'
+            date_from=datetime(2024, 12, 1, 9, 0, 0, tzinfo=timezone.utc),
+            plugins='pretix.plugins.banktransfer'
         )
         o = Order.objects.create(
             code='FOO', event=event, email='dummy@dummy.test',
@@ -660,3 +662,154 @@ def test_addon_aware_groupby():
             [True, 102, 3.00],
         ]],
     ]
+
+
+@pytest.mark.django_db
+@pytest.mark.parametrize("period", ["auto", "event_date"])
+def test_period_from_event_start(env, period):
+    event, order = env
+    event.settings.invoice_period = period
+    inv = generate_invoice(order)
+    l1 = inv.lines.first()
+    assert l1.period_start == event.date_from
+    assert l1.period_end == event.date_from
+
+
+@pytest.mark.django_db
+@pytest.mark.parametrize("period", ["auto", "event_date"])
+def test_period_from_event_range(env, period):
+    event, order = env
+    event.date_to = event.date_from + timedelta(days=1)
+    event.settings.invoice_period = period
+    inv = generate_invoice(order)
+    l1 = inv.lines.first()
+    assert l1.period_start == event.date_from
+    assert l1.period_end == event.date_to
+
+
+@pytest.mark.django_db
+@pytest.mark.parametrize("period", ["auto", "auto_no_event"])
+def test_period_from_ticket_validity(env, period):
+    event, order = env
+    p1 = order.positions.first()
+    p1.valid_from = datetime(2025, 1, 1, 0, 0, 0, tzinfo=event.timezone)
+    p1.valid_until = datetime(2025, 12, 31, 23, 59, 59, tzinfo=event.timezone)
+    p1.save()
+    event.date_to = event.date_from + timedelta(days=1)
+    event.settings.invoice_period = period
+    inv = generate_invoice(order)
+    l1 = inv.lines.first()
+    assert l1.period_start == p1.valid_from
+    assert l1.period_end == p1.valid_until
+
+
+@pytest.mark.django_db
+@pytest.mark.parametrize("period", ["auto", "auto_no_event"])
+def test_period_from_subevent(env, period):
+    event, order = env
+    event.has_subevents = True
+    event.save()
+    se1 = event.subevents.create(
+        name=event.name,
+        active=True,
+        date_from=datetime((now().year + 1), 7, 31, 9, 0, 0, tzinfo=timezone.utc),
+        date_to=datetime((now().year + 1), 7, 31, 17, 0, 0, tzinfo=timezone.utc),
+    )
+    p1 = order.positions.first()
+    p1.subevent = se1
+    p1.save()
+    event.date_to = event.date_from + timedelta(days=1)
+    event.settings.invoice_period = period
+    inv = generate_invoice(order)
+    l1 = inv.lines.first()
+    assert l1.period_start == se1.date_from
+    assert l1.period_end == se1.date_to
+
+
+@pytest.mark.django_db
+@pytest.mark.parametrize("period", ["auto", "auto_no_event"])
+def test_period_from_memberships(env, period):
+    event, order = env
+    event.date_to = event.date_from + timedelta(days=1)
+    event.settings.invoice_period = period
+    p1 = order.positions.first()
+    membershiptype = event.organizer.membership_types.create(
+        name=LazyI18nString({"en": "Week pass"}),
+        transferable=True,
+        allow_parallel_usage=False,
+        max_usages=15,
+    )
+    customer = event.organizer.customers.create(
+        identifier="8WSAJCJ",
+        email="foo@example.org",
+        name_parts={"_legacy": "Foo"},
+        name_cached="Foo",
+        is_verified=False,
+    )
+    m = customer.memberships.create(
+        membership_type=membershiptype,
+        granted_in=p1,
+        date_start=datetime(2021, 4, 1, 0, 0, 0, 0, tzinfo=timezone.utc),
+        date_end=datetime(2021, 4, 8, 23, 59, 59, 999999, tzinfo=timezone.utc),
+        attendee_name_parts={
+            "_scheme": "given_family",
+            'given_name': 'John',
+            'family_name': 'Doe',
+        }
+    )
+    inv = generate_invoice(order)
+    l1 = inv.lines.first()
+    assert l1.period_start == m.date_start
+    assert l1.period_end == m.date_end
+
+
+@pytest.mark.django_db
+def test_period_auto_no_event_from_invoice(env):
+    event, order = env
+    event.settings.invoice_period = "auto_no_event"
+    inv = generate_invoice(order)
+    l1 = inv.lines.first()
+    assert abs(l1.period_start - now()) < timedelta(seconds=10)
+    assert abs(l1.period_end - now()) < timedelta(seconds=10)
+
+
+@pytest.mark.django_db
+def test_period_always_invoice_date(env):
+    event, order = env
+    p1 = order.positions.first()
+    p1.valid_from = datetime(2025, 1, 1, 0, 0, 0, tzinfo=event.timezone)
+    p1.valid_until = datetime(2025, 12, 31, 23, 59, 59, tzinfo=event.timezone)
+    p1.save()
+    event.settings.invoice_period = "invoice_date"
+    inv = generate_invoice(order)
+    l1 = inv.lines.first()
+    assert abs(l1.period_start - now()) < timedelta(seconds=10)
+    assert abs(l1.period_end - now()) < timedelta(seconds=10)
+
+
+@pytest.mark.django_db
+def test_period_always_event_date(env):
+    event, order = env
+    p1 = order.positions.first()
+    p1.valid_from = datetime(2025, 1, 1, 0, 0, 0, tzinfo=event.timezone)
+    p1.valid_until = datetime(2025, 12, 31, 23, 59, 59, tzinfo=event.timezone)
+    p1.save()
+    event.settings.invoice_period = "event_date"
+    inv = generate_invoice(order)
+    l1 = inv.lines.first()
+    assert l1.period_start == event.date_from
+    assert l1.period_end == event.date_from
+
+
+@pytest.mark.django_db
+def test_period_always_order_date(env):
+    event, order = env
+    p1 = order.positions.first()
+    p1.valid_from = datetime(2025, 1, 1, 0, 0, 0, tzinfo=event.timezone)
+    p1.valid_until = datetime(2025, 12, 31, 23, 59, 59, tzinfo=event.timezone)
+    p1.save()
+    event.settings.invoice_period = "order_date"
+    inv = generate_invoice(order)
+    l1 = inv.lines.first()
+    assert l1.period_start == order.datetime
+    assert l1.period_end == order.datetime