TaxRules: Add internal_name and keep_gross_if_rate_changes (#2422)

Co-authored-by: ser8phin <eva.wolkwitz@gmx.de>

src/pretix/base/migrations/0207_auto_20220119_1427.py

@@ -0,0 +1,23 @@
+# Generated by Django 3.2.4 on 2022-01-19 14:27
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('pretixbase', '0206_customer_phone'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='taxrule',
+            name='internal_name',
+            field=models.CharField(max_length=190, null=True),
+        ),
+        migrations.AddField(
+            model_name='taxrule',
+            name='keep_gross_if_rate_changes',
+            field=models.BooleanField(default=False),
+        ),
+    ]

src/pretix/base/models/tax.py

@@ -81,6 +81,15 @@ class TaxedPrice:
             name=self.name,
         )
 
+    def __eq__(self, other):
+        return (
+            self.gross == other.gross and
+            self.net == other.net and
+            self.tax == other.tax and
+            self.rate == other.rate and
+            self.name == other.name
+        )
+
 
 TAXED_ZERO = TaxedPrice(
     gross=Decimal('0.00'),
@@ -127,8 +136,13 @@ def cc_to_vat_prefix(country_code):
 
 class TaxRule(LoggedModel):
     event = models.ForeignKey('Event', related_name='tax_rules', on_delete=models.CASCADE)
+    internal_name = models.CharField(
+        verbose_name=_('Internal name'),
+        max_length=190,
+        null=True, blank=True,
+    )
     name = I18nCharField(
-        verbose_name=_('Name'),
+        verbose_name=_('Official name'),
         help_text=_('Should be short, e.g. "VAT"'),
         max_length=190,
     )
@@ -141,6 +155,10 @@ class TaxRule(LoggedModel):
         verbose_name=_("The configured product prices include the tax amount"),
         default=True,
     )
+    keep_gross_if_rate_changes = models.BooleanField(
+        verbose_name=_("Keep gross amount constant if the tax rate changes based on the invoice address"),
+        default=False,
+    )
     eu_reverse_charge = models.BooleanField(
         verbose_name=_("Use EU reverse charge taxation rules"),
         default=False,
@@ -198,6 +216,8 @@ class TaxRule(LoggedModel):
             s = _('plus {rate}% {name}').format(rate=self.rate, name=self.name)
         if self.eu_reverse_charge:
             s += ' ({})'.format(_('reverse charge enabled'))
+        if self.internal_name:
+            return f'{self.internal_name} ({s})'
         return str(s)
 
     @property
@@ -228,13 +248,19 @@ class TaxRule(LoggedModel):
             rate = override_tax_rate
         elif invoice_address:
             adjust_rate = self.tax_rate_for(invoice_address)
-            if (adjust_rate == gross_price_is_tax_rate or force_fixed_gross_price) and base_price_is == 'gross':
+            if (adjust_rate == gross_price_is_tax_rate or force_fixed_gross_price or self.keep_gross_if_rate_changes) and base_price_is == 'gross':
                 rate = adjust_rate
             elif adjust_rate != rate:
-                normal_price = self.tax(base_price, base_price_is, currency, subtract_from_gross=subtract_from_gross)
-                base_price = normal_price.net
-                base_price_is = 'net'
-                subtract_from_gross = Decimal('0.00')
+                if self.keep_gross_if_rate_changes:
+                    normal_price = self.tax(base_price, base_price_is, currency, subtract_from_gross=subtract_from_gross)
+                    base_price = normal_price.gross
+                    base_price_is = 'gross'
+                    subtract_from_gross = Decimal('0.00')
+                else:
+                    normal_price = self.tax(base_price, base_price_is, currency, subtract_from_gross=subtract_from_gross)
+                    base_price = normal_price.net
+                    base_price_is = 'net'
+                    subtract_from_gross = Decimal('0.00')
                 rate = adjust_rate
 
         if rate == Decimal('0.00'):

src/pretix/base/services/cart.py

@@ -426,10 +426,10 @@ class CartManager:
                 if not cp.includes_tax:
                     price = self._get_price(cp.item, cp.variation, cp.voucher, cp.price, cp.subevent,
                                             cp_is_net=True, bundled_sum=bundled_sum)
-                    price = TaxedPrice(net=price.net, gross=price.net, rate=0, tax=0, name='')
+                    price = TaxedPrice(net=price.net, gross=price.net, rate=Decimal('0'), tax=Decimal('0'), name='')
                     pbv = self._get_price(cp.item, cp.variation, None, cp.price, cp.subevent,
                                           cp_is_net=True, bundled_sum=bundled_sum)
-                    pbv = TaxedPrice(net=pbv.net, gross=pbv.net, rate=0, tax=0, name='')
+                    pbv = TaxedPrice(net=pbv.net, gross=pbv.net, rate=Decimal('0'), tax=Decimal('0'), name='')
                 else:
                     price = self._get_price(cp.item, cp.variation, cp.voucher, cp.price, cp.subevent,
                                             bundled_sum=bundled_sum)
@@ -1106,10 +1106,11 @@ def update_tax_rates(event: Event, cart_id: str, invoice_address: InvoiceAddress
         rate = pos.item.tax_rule.tax_rate_for(invoice_address)
 
         if pos.tax_rate != rate:
-            current_net = pos.price - pos.tax_value
-            new_gross = pos.item.tax(current_net, base_price_is='net', invoice_address=invoice_address).gross
-            totaldiff += new_gross - pos.price
-            pos.price = new_gross
+            if not pos.item.tax_rule.keep_gross_if_rate_changes:
+                current_net = pos.price - pos.tax_value
+                new_gross = pos.item.tax(current_net, base_price_is='net', invoice_address=invoice_address).gross
+                totaldiff += new_gross - pos.price
+                pos.price = new_gross
             pos.includes_tax = rate != Decimal('0.00')
             pos.override_tax_rate = rate
             pos.save(update_fields=['price', 'includes_tax', 'override_tax_rate'])

src/pretix/base/services/orders.py

@@ -700,7 +700,7 @@ def _check_positions(event: Event, now_dt: datetime, positions: List[CartPositio
                                 invoice_address=address, force_custom_price=True, max_discount=max_discount)
                 changed_prices[cp.pk] = bprice
             else:
-                bundled_sum = 0
+                bundled_sum = Decimal('0.00')
                 if not cp.addon_to_id:
                     for bundledp in cp.addons.all():
                         if bundledp.is_bundled: