diff --git a/src/pretix/api/views/order.py b/src/pretix/api/views/order.py
index 9076e4b36b..0ae20342c8 100644
--- a/src/pretix/api/views/order.py
+++ b/src/pretix/api/views/order.py
@@ -148,9 +148,13 @@ with scopes_disabled():
             else:
                 code = Q(code__icontains=Order.normalize_code(u))
 
+            invoice_nos = {u, u.upper()}
+            if u.isdigit():
+                for i in range(2, 12):
+                    invoice_nos.add(u.zfill(i))
+
             matching_invoices = Invoice.objects.filter(
-                Q(invoice_no__iexact=u)
-                | Q(invoice_no__iexact=u.zfill(5))
+                Q(invoice_no__in=invoice_nos)
                 | Q(full_invoice_no__iexact=u)
             ).values_list('order_id', flat=True)
 
diff --git a/src/pretix/base/settings.py b/src/pretix/base/settings.py
index f11c78b956..4137ed3d74 100644
--- a/src/pretix/base/settings.py
+++ b/src/pretix/base/settings.py
@@ -594,6 +594,7 @@ DEFAULTS = {
         'form_kwargs': dict(
             label=_("Minimum length of invoice number after prefix"),
             help_text=_("The part of your invoice number after your prefix will be filled up with leading zeros up to this length, e.g. INV-001 or INV-00001."),
+            max_value=12,
             required=True,
         )
     },
diff --git a/src/pretix/control/forms/filter.py b/src/pretix/control/forms/filter.py
index 06c2ea755d..6a34e6fbfb 100644
--- a/src/pretix/control/forms/filter.py
+++ b/src/pretix/control/forms/filter.py
@@ -256,9 +256,13 @@ class OrderFilterForm(FilterForm):
             else:
                 code = Q(code__icontains=Order.normalize_code(u))
 
+            invoice_nos = {u, u.upper()}
+            if u.isdigit():
+                for i in range(2, 12):
+                    invoice_nos.add(u.zfill(i))
+
             matching_invoices = Invoice.objects.filter(
-                Q(invoice_no__iexact=u)
-                | Q(invoice_no__iexact=u.zfill(5))
+                Q(invoice_no__in=invoice_nos)
                 | Q(full_invoice_no__iexact=u)
             ).values_list('order_id', flat=True)
             matching_positions = OrderPosition.objects.filter(
@@ -1004,9 +1008,13 @@ class OrderPaymentSearchFilterForm(forms.Form):
         if fdata.get('query'):
             u = fdata.get('query')
 
+            invoice_nos = {u, u.upper()}
+            if u.isdigit():
+                for i in range(2, 12):
+                    invoice_nos.add(u.zfill(i))
+
             matching_invoices = Invoice.objects.filter(
-                Q(invoice_no__iexact=u)
-                | Q(invoice_no__iexact=u.zfill(5))
+                Q(invoice_no__in=invoice_nos)
                 | Q(full_invoice_no__iexact=u)
             ).values_list('order_id', flat=True)
 
diff --git a/src/pretix/plugins/banktransfer/views.py b/src/pretix/plugins/banktransfer/views.py
index 49ee14852f..7e78c9ab24 100644
--- a/src/pretix/plugins/banktransfer/views.py
+++ b/src/pretix/plugins/banktransfer/views.py
@@ -46,7 +46,6 @@ from django import forms
 from django.contrib import messages
 from django.db import transaction
 from django.db.models import Count, Q, QuerySet
-from django.db.models.functions import Concat
 from django.http import FileResponse, JsonResponse
 from django.shortcuts import get_object_or_404, redirect, render
 from django.urls import reverse
@@ -247,16 +246,24 @@ class ActionView(View):
                     & Q(code__icontains=Order.normalize_code(u.split("-")[1])))
         else:
             code = Q(code__icontains=Order.normalize_code(u))
-        qs = self.order_qs().order_by('pk').annotate(inr=Concat('invoices__prefix', 'invoices__invoice_no')).filter(
+
+        invoice_nos = {u, u.upper()}
+        if u.isdigit():
+            if hasattr(request, 'event'):
+                invoice_nos.add(u.zfill(request.event.invoice_numbers_counter_length))
+            else:
+                for i in range(2, 12):
+                    invoice_nos.add(u.zfill(i))
+
+        qs = self.order_qs().order_by('pk').filter(
             code
             | Q(email__icontains=u)
             | Q(all_positions__attendee_name_cached__icontains=u)
             | Q(all_positions__attendee_email__icontains=u)
             | Q(invoice_address__name_cached__icontains=u)
             | Q(invoice_address__company__icontains=u)
-            | Q(invoices__invoice_no=u)
-            | Q(invoices__invoice_no=u.zfill(5))
-            | Q(inr=u)
+            | Q(invoices__invoice_no__in=invoice_nos)
+            | Q(invoices__full_invoice_no=u)
         ).select_related('event').annotate(pcnt=Count('invoices')).distinct()
         # Yep, we wouldn't need to count the invoices here. However, having this Count() statement in there
         # tricks Django into generating a GROUP BY clause that it otherwise wouldn't and that is required to