Order change interface: Fix taxation edge case

src/pretix/control/forms/orders.py

@@ -292,10 +292,7 @@ class OrderPositionChangeForm(forms.Form):
         instance = kwargs.pop('instance')
         initial = kwargs.get('initial', {})
 
-        if instance.item.tax_rule and not instance.item.tax_rule.price_includes_tax:
-            initial['price'] = instance.price - instance.tax_value
-        else:
-            initial['price'] = instance.price
+        initial['price'] = instance.price
 
         kwargs['initial'] = initial
         super().__init__(*args, **kwargs)

src/pretix/control/templates/pretixcontrol/order/change.html

@@ -121,11 +121,13 @@
                                 <strong>{% trans "Price" %}</strong>
                             </div>
                             <div class="col-sm-5">
-                                {{ position.price|money:request.event.currency }}<br>
+                                {{ position.price|money:request.event.currency }}
                                 {% if position.tax_rate %}
-                                    <small>{% blocktrans trimmed with rate=position.tax_rate name=position.tax_rule.name %}
-                                        <strong>incl.</strong> {{ rate }}% {{ name }}
-                                    {% endblocktrans %}</small>
+                                    <br>
+                                    <small>
+                                        ({{ position.net_price|money:request.event.currency }}
+                                        + {{ position.tax_rate }}%)
+                                    </small>
                                 {% endif %}
                             </div>
                             <div class="col-sm-4 field-container">