diff --git a/src/pretix/base/models/vouchers.py b/src/pretix/base/models/vouchers.py
index ced25aa82..34991aa5b 100644
--- a/src/pretix/base/models/vouchers.py
+++ b/src/pretix/base/models/vouchers.py
@@ -25,7 +25,7 @@ def _generate_random_code(prefix=None):
 def generate_code(prefix=None):
     while True:
         code = _generate_random_code(prefix=prefix)
-        if not Voucher.objects.filter(code=code).exists():
+        if not Voucher.objects.filter(code__iexact=code).exists():
             return code
 
 
@@ -278,11 +278,9 @@ class Voucher(LoggedModel):
             if old_instance.quota:
                 quotas.add(old_instance.quota)
             elif old_instance.variation:
-                quotas |= set(old_instance.variation.quotas.filter(
-                    subevent=old_instance.subevent))
+                quotas |= set(old_instance.variation.quotas.filter(subevent=old_instance.subevent))
             elif old_instance.item:
-                quotas |= set(old_instance.item.quotas.filter(
-                    subevent=old_instance.subevent))
+                quotas |= set(old_instance.item.quotas.filter(subevent=old_instance.subevent))
         return quotas
 
     @staticmethod
@@ -313,7 +311,7 @@ class Voucher(LoggedModel):
 
     @staticmethod
     def clean_voucher_code(data, event, pk):
-        if 'code' in data and Voucher.objects.filter(Q(code=data['code']) & Q(event=event) & ~Q(pk=pk)).exists():
+        if 'code' in data and Voucher.objects.filter(Q(code__iexact=data['code']) & Q(event=event) & ~Q(pk=pk)).exists():
             raise ValidationError(_('A voucher with this code already exists.'))
 
     def save(self, *args, **kwargs):
diff --git a/src/pretix/base/services/cart.py b/src/pretix/base/services/cart.py
index 94cdb481d..58debd723 100644
--- a/src/pretix/base/services/cart.py
+++ b/src/pretix/base/services/cart.py
@@ -295,7 +295,7 @@ class CartManager:
 
             if i.get('voucher'):
                 try:
-                    voucher = self.event.vouchers.get(code=i.get('voucher').strip())
+                    voucher = self.event.vouchers.get(code__iexact=i.get('voucher').strip())
                 except Voucher.DoesNotExist:
                     raise CartError(error_messages['voucher_invalid'])
                 else:
diff --git a/src/pretix/control/forms/vouchers.py b/src/pretix/control/forms/vouchers.py
index 6b85ea1d7..633e24651 100644
--- a/src/pretix/control/forms/vouchers.py
+++ b/src/pretix/control/forms/vouchers.py
@@ -2,6 +2,7 @@ import copy
 
 from django import forms
 from django.core.exceptions import ValidationError
+from django.db.models.functions import Lower
 from django.utils.translation import ugettext_lazy as _
 
 from pretix.base.forms import I18nModelForm
@@ -164,7 +165,10 @@ class VoucherBulkForm(VoucherForm):
     def clean(self):
         data = super().clean()
 
-        if Voucher.objects.filter(code__in=data['codes'], event=self.instance.event).exists():
+        vouchers = self.instance.event.vouchers.annotate(
+            code_lower=Lower('code')
+        ).filter(code_lower__in=[c.lower() for c in data['codes']])
+        if vouchers.exists():
             raise ValidationError(_('A voucher with one of these codes already exists.'))
 
         return data
diff --git a/src/pretix/presale/views/cart.py b/src/pretix/presale/views/cart.py
index a41e4b914..47cb656fa 100644
--- a/src/pretix/presale/views/cart.py
+++ b/src/pretix/presale/views/cart.py
@@ -399,7 +399,7 @@ class RedeemView(NoSearchIndexViewMixin, EventViewMixin, TemplateView):
         if v:
             v = v.strip()
             try:
-                self.voucher = Voucher.objects.get(code=v, event=request.event)
+                self.voucher = Voucher.objects.get(code__iexact=v, event=request.event)
                 if self.voucher.redeemed >= self.voucher.max_usages:
                     err = error_messages['voucher_redeemed']
                 if self.voucher.valid_until is not None and self.voucher.valid_until < now():
diff --git a/src/pretix/presale/views/widget.py b/src/pretix/presale/views/widget.py
index 5b61ebc52..a7d62eac5 100644
--- a/src/pretix/presale/views/widget.py
+++ b/src/pretix/presale/views/widget.py
@@ -238,7 +238,7 @@ class WidgetAPIProductList(View):
         self.voucher = None
         if 'voucher' in request.GET:
             try:
-                self.voucher = request.event.vouchers.get(code=request.GET.get('voucher').strip())
+                self.voucher = request.event.vouchers.get(code__iexact=request.GET.get('voucher').strip())
                 if self.voucher.redeemed >= self.voucher.max_usages:
                     data['error'] = error_messages['voucher_redeemed']
                     fail = True