diff --git a/docs/installation/upgrade-300.rst b/docs/installation/upgrade-300.rst
index 6f0a677cb0..36d4aca212 100644
--- a/docs/installation/upgrade-300.rst
+++ b/docs/installation/upgrade-300.rst
@@ -74,3 +74,10 @@ StUF-ZDS payments extension conversion
 The import conversion of StUF-ZDS plugin extensions, back to the default StUF-ZDS plugin,
 has been removed. We recommend re-creating the exports on a newer version of Open Forms,
 or manually changing the plugin to `stuf-zds-create-zaak` in the export files.
+
+Removal of single registration conversion
+-----------------------------------------
+
+The legacy format (from before Open Forms 2.3) for registration backend will no longer be
+converted to the current standard. When importing a form with this configuration,
+the form will be created without registration backends.
diff --git a/src/openapi.yaml b/src/openapi.yaml
index 1d81cf358d..7fdfc19896 100644
--- a/src/openapi.yaml
+++ b/src/openapi.yaml
@@ -1325,8 +1325,6 @@ paths:
 
         - `internalName`
         - `registrationBackends`
-        - `registrationBackend`
-        - `registrationBackendOptions`
         - `authenticationBackendOptions`
         - `paymentBackend`
         - `paymentBackendOptions`
@@ -1399,8 +1397,6 @@ paths:
 
         - `internalName`
         - `registrationBackends`
-        - `registrationBackend`
-        - `registrationBackendOptions`
         - `authenticationBackendOptions`
         - `paymentBackend`
         - `paymentBackendOptions`
@@ -1917,8 +1913,6 @@ paths:
 
         - `internalName`
         - `registrationBackends`
-        - `registrationBackend`
-        - `registrationBackendOptions`
         - `authenticationBackendOptions`
         - `paymentBackend`
         - `paymentBackendOptions`
@@ -1997,8 +1991,6 @@ paths:
 
         - `internalName`
         - `registrationBackends`
-        - `registrationBackend`
-        - `registrationBackendOptions`
         - `authenticationBackendOptions`
         - `paymentBackend`
         - `paymentBackendOptions`
@@ -2081,8 +2073,6 @@ paths:
 
         - `internalName`
         - `registrationBackends`
-        - `registrationBackend`
-        - `registrationBackendOptions`
         - `authenticationBackendOptions`
         - `paymentBackend`
         - `paymentBackendOptions`
@@ -7564,7 +7554,7 @@ components:
 
         Note that this schema is used for both non-admin users filling out forms and
         admin users designing forms. The fields that are only relevant for admin users are:
-        `internalName`, `registrationBackends`, `registrationBackend`, `registrationBackendOptions`, `authenticationBackendOptions`, `paymentBackend`, `paymentBackendOptions`, `priceVariableKey`, `product`, `category`, `theme`, `activateOn`, `deactivateOn`, `isDeleted`, `submissionConfirmationTemplate`, `askPrivacyConsent`, `askStatementOfTruth`, `submissionsRemovalOptions`, `confirmationEmailTemplate`, `sendConfirmationEmail`, `displayMainWebsiteLink`, `includeConfirmationPageContentInPdf`, `translations`, `brpPersonenRequestOptions`.
+        `internalName`, `registrationBackends`, `authenticationBackendOptions`, `paymentBackend`, `paymentBackendOptions`, `priceVariableKey`, `product`, `category`, `theme`, `activateOn`, `deactivateOn`, `isDeleted`, `submissionConfirmationTemplate`, `askPrivacyConsent`, `askStatementOfTruth`, `submissionsRemovalOptions`, `confirmationEmailTemplate`, `sendConfirmationEmail`, `displayMainWebsiteLink`, `includeConfirmationPageContentInPdf`, `translations`, `brpPersonenRequestOptions`.
       properties:
         uuid:
           type: string
@@ -7586,12 +7576,6 @@ components:
           type: array
           items:
             $ref: '#/components/schemas/FormRegistrationBackend'
-        registrationBackend:
-          type: string
-          deprecated: true
-        registrationBackendOptions:
-          nullable: true
-          deprecated: true
         authenticationBackends:
           type: array
           items:
@@ -8077,7 +8061,7 @@ components:
 
         Note that this schema is used for both non-admin users filling out forms and
         admin users designing forms. The fields that are only relevant for admin users are:
-        `internalName`, `registrationBackends`, `registrationBackend`, `registrationBackendOptions`, `authenticationBackendOptions`, `paymentBackend`, `paymentBackendOptions`, `priceVariableKey`, `product`, `category`, `theme`, `activateOn`, `deactivateOn`, `isDeleted`, `submissionConfirmationTemplate`, `askPrivacyConsent`, `askStatementOfTruth`, `submissionsRemovalOptions`, `confirmationEmailTemplate`, `sendConfirmationEmail`, `displayMainWebsiteLink`, `includeConfirmationPageContentInPdf`, `translations`, `brpPersonenRequestOptions`.
+        `internalName`, `registrationBackends`, `authenticationBackendOptions`, `paymentBackend`, `paymentBackendOptions`, `priceVariableKey`, `product`, `category`, `theme`, `activateOn`, `deactivateOn`, `isDeleted`, `submissionConfirmationTemplate`, `askPrivacyConsent`, `askStatementOfTruth`, `submissionsRemovalOptions`, `confirmationEmailTemplate`, `sendConfirmationEmail`, `displayMainWebsiteLink`, `includeConfirmationPageContentInPdf`, `translations`, `brpPersonenRequestOptions`.
       properties:
         name:
           type: string
@@ -8248,7 +8232,7 @@ components:
 
         Note that this schema is used for both non-admin users filling out forms and
         admin users designing forms. The fields that are only relevant for admin users are:
-        `internalName`, `registrationBackends`, `registrationBackend`, `registrationBackendOptions`, `authenticationBackendOptions`, `paymentBackend`, `paymentBackendOptions`, `priceVariableKey`, `product`, `category`, `theme`, `activateOn`, `deactivateOn`, `isDeleted`, `submissionConfirmationTemplate`, `askPrivacyConsent`, `askStatementOfTruth`, `submissionsRemovalOptions`, `confirmationEmailTemplate`, `sendConfirmationEmail`, `displayMainWebsiteLink`, `includeConfirmationPageContentInPdf`, `translations`, `brpPersonenRequestOptions`.
+        `internalName`, `registrationBackends`, `authenticationBackendOptions`, `paymentBackend`, `paymentBackendOptions`, `priceVariableKey`, `product`, `category`, `theme`, `activateOn`, `deactivateOn`, `isDeleted`, `submissionConfirmationTemplate`, `askPrivacyConsent`, `askStatementOfTruth`, `submissionsRemovalOptions`, `confirmationEmailTemplate`, `sendConfirmationEmail`, `displayMainWebsiteLink`, `includeConfirmationPageContentInPdf`, `translations`, `brpPersonenRequestOptions`.
       properties:
         name:
           type: string
@@ -9182,7 +9166,7 @@ components:
 
         Note that this schema is used for both non-admin users filling out forms and
         admin users designing forms. The fields that are only relevant for admin users are:
-        `internalName`, `registrationBackends`, `registrationBackend`, `registrationBackendOptions`, `authenticationBackendOptions`, `paymentBackend`, `paymentBackendOptions`, `priceVariableKey`, `product`, `category`, `theme`, `activateOn`, `deactivateOn`, `isDeleted`, `submissionConfirmationTemplate`, `askPrivacyConsent`, `askStatementOfTruth`, `submissionsRemovalOptions`, `confirmationEmailTemplate`, `sendConfirmationEmail`, `displayMainWebsiteLink`, `includeConfirmationPageContentInPdf`, `translations`, `brpPersonenRequestOptions`.
+        `internalName`, `registrationBackends`, `authenticationBackendOptions`, `paymentBackend`, `paymentBackendOptions`, `priceVariableKey`, `product`, `category`, `theme`, `activateOn`, `deactivateOn`, `isDeleted`, `submissionConfirmationTemplate`, `askPrivacyConsent`, `askStatementOfTruth`, `submissionsRemovalOptions`, `confirmationEmailTemplate`, `sendConfirmationEmail`, `displayMainWebsiteLink`, `includeConfirmationPageContentInPdf`, `translations`, `brpPersonenRequestOptions`.
       properties:
         uuid:
           type: string
@@ -9204,12 +9188,6 @@ components:
           type: array
           items:
             $ref: '#/components/schemas/FormRegistrationBackend'
-        registrationBackend:
-          type: string
-          deprecated: true
-        registrationBackendOptions:
-          nullable: true
-          deprecated: true
         authenticationBackends:
           type: array
           items:
diff --git a/src/openforms/fixtures/demo.json b/src/openforms/fixtures/demo.json
index 3ff026dbf9..4d6e6ed41e 100644
--- a/src/openforms/fixtures/demo.json
+++ b/src/openforms/fixtures/demo.json
@@ -7,8 +7,7 @@
         "name": "\u2615\ufe0f",
         "slug": "koffie",
         "active": true,
-        "product": null,
-        "registration_backend": "openforms.core.backends.console_backend"
+        "product": null
     }
 },
 {
@@ -19,8 +18,18 @@
         "name": "Demo multiple steps",
         "slug": "demo-multiple-steps",
         "active": true,
-        "product": null,
-        "registration_backend": ""
+        "product": null
+    }
+},
+{
+    "model": "forms.form_formregistrationbackend",
+    "pk": 1,
+    "fields": {
+        "key": "backend",
+        "name": "backend",
+        "backend": "openforms.core.backends.console_backend",
+        "options": {},
+        "form": 1
     }
 },
 {
diff --git a/src/openforms/forms/api/serializers/form.py b/src/openforms/forms/api/serializers/form.py
index 07c938a3b1..cbaa1b4bc8 100644
--- a/src/openforms/forms/api/serializers/form.py
+++ b/src/openforms/forms/api/serializers/form.py
@@ -1,5 +1,3 @@
-import warnings
-
 from django.db import transaction
 from django.utils.translation import gettext_lazy as _
 
@@ -100,8 +98,6 @@ def validate(self, attrs):
 
 @extend_schema_serializer(
     deprecate_fields=[
-        "registration_backend",
-        "registration_backend_options",
         "cosign_login_info",
     ]
 )
@@ -224,12 +220,6 @@ class FormSerializer(PublicFieldsSerializerMixin, serializers.ModelSerializer):
 
     registration_backends = FormRegistrationBackendSerializer(many=True, required=False)
 
-    # deprecated fields
-    registration_backend = serializers.CharField(required=False, allow_blank=True)
-    registration_backend_options = serializers.JSONField(
-        required=False, allow_null=True
-    )
-
     class Meta:
         model = Form
         fields = (
@@ -239,8 +229,6 @@ class Meta:
             "login_required",
             "translation_enabled",
             "registration_backends",
-            "registration_backend",
-            "registration_backend_options",
             "authentication_backends",
             "authentication_backend_options",
             "login_options",
@@ -342,26 +330,6 @@ def create(self, validated_data):
         )
         registration_backends = validated_data.pop("registration_backends", [])
 
-        registration_backend_options = (
-            validated_data.pop("registration_backend_options", None) or {}
-        )
-        if "registration_backend" in validated_data:
-            warnings.warn(
-                (
-                    "Form 'registration_backend' and 'registration_backend_options' "
-                    "are deprecated, use 'registration_backends' instead."
-                ),
-                DeprecationWarning,
-            )
-            registration_backends.append(
-                {
-                    "key": "default",
-                    "name": _("Default"),
-                    "backend": validated_data.pop("registration_backend"),
-                    "options": registration_backend_options,
-                }
-            )
-
         instance = super().create(validated_data)
         ConfirmationEmailTemplate.objects.set_for_form(
             form=instance, data=confirmation_email_template
@@ -376,33 +344,6 @@ def create(self, validated_data):
         )
         return instance
 
-    def _update_v2_registration_backend(self, form, validated_data):
-        new_data = {}
-        if "registration_backend" in validated_data:
-            new_data["backend"] = validated_data.pop("registration_backend")
-        if "registration_backend_options" in validated_data:
-            new_data["options"] = validated_data.pop("registration_backend_options")
-        if not any(v is not None for v in new_data.values()):
-            return
-
-        warnings.warn(
-            (
-                "Form 'registration_backend' and 'registration_backend_options' "
-                "are deprecated, use 'registration_backends' instead."
-            ),
-            DeprecationWarning,
-        )
-
-        backend = form.registration_backends.first() or FormRegistrationBackend(
-            form=form, name=_("Default"), key="default"
-        )
-        serializer = FormRegistrationBackendSerializer(
-            instance=backend, data=new_data, context=self.context, partial=self.partial
-        )
-        # validated_data ought to be correct already
-        assert serializer.is_valid()
-        serializer.save()
-
     @transaction.atomic()
     def update(self, instance, validated_data):
         confirmation_email_template = validated_data.pop(
@@ -413,8 +354,6 @@ def update(self, instance, validated_data):
         )
         registration_backends = validated_data.pop("registration_backends", None)
 
-        self._update_v2_registration_backend(instance, validated_data)
-
         instance = super().update(instance, validated_data)
         ConfirmationEmailTemplate.objects.set_for_form(
             form=instance, data=confirmation_email_template
@@ -446,43 +385,11 @@ def get_fields(self):
                 ("", "")
             ] + payment_register.get_choices()
 
-        # adapt fields for v2 backwards compatibility
-        if "registration_backends" in fields:
-            v2_backend = fields["registration_backend"]
-            v3_backend = fields["registration_backends"].child.get_fields()["backend"]
-            v2_backend.choices = v3_backend.choices
-
         return fields
 
     def validate(self, attrs):
         super().validate(attrs)
 
-        if "registration_backend" in attrs and "registration_backends" in attrs:
-            raise serializers.ValidationError(
-                {
-                    "registration_backend": ErrorDetail(
-                        _(
-                            "registration_backend is deprecated, please use just registration_backends",
-                        ),
-                        code="invalid",
-                    ),
-                    "registration_backend_options": ErrorDetail(
-                        _(
-                            "registration_backend is deprecated, please use just registration_backends",
-                        ),
-                        code="invalid",
-                    ),
-                }
-            )
-
-        if "registration_backends" not in attrs:
-            self.validate_backend_options(
-                attrs,
-                "registration_backend",
-                "registration_backend_options",
-                registration_register,
-            )
-
         self.validate_backend_options(
             attrs, "payment_backend", "payment_backend_options", payment_register
         )
@@ -509,7 +416,7 @@ def validate_backend_options(self, attrs, backend_field, options_field, registry
         except serializers.ValidationError as e:
             # wrap detail in dict so we can attach it to the field
             # DRF will create the .invalidParams with a dotted path to nested fields
-            # like registrationBackendOptions.toEmails.0 if the first email was invalid
+            # like registrationBackends.0.options.toEmails.0 if the first email was invalid
             detail = {options_field: e.detail}
             raise serializers.ValidationError(detail) from e
         # serializer does some normalization, so make sure to update the data
@@ -623,10 +530,6 @@ def get_fields(self):
             del fields["payment_options"]
         if "authentication_backends" in fields:
             fields["authentication_backends"].write_only = False
-        if "registration_backend" in fields:
-            del fields["registration_backend"]
-        if "registration_backend_options" in fields:
-            del fields["registration_backend_options"]
         return fields
 
 
diff --git a/src/openforms/forms/models/form.py b/src/openforms/forms/models/form.py
index b08c994c73..fc795376c6 100644
--- a/src/openforms/forms/models/form.py
+++ b/src/openforms/forms/models/form.py
@@ -394,20 +394,6 @@ def get_absolute_url(self):
     def get_api_url(self):
         return reverse("api:form-detail", kwargs={"uuid": self.uuid})
 
-    @property
-    def registration_backend(self) -> str | None:
-        "For backwards compatibility"
-        return (
-            backend.backend if (backend := self.registration_backends.first()) else None
-        )
-
-    @property
-    def registration_backend_options(self) -> str | None:
-        "For backwards compatibility"
-        return (
-            backend.options if (backend := self.registration_backends.first()) else None
-        )
-
     def get_registration_backend_display(self) -> str:
         return (
             ", ".join(
diff --git a/src/openforms/forms/tests/test_api_form_plugin_options.py b/src/openforms/forms/tests/test_api_form_plugin_options.py
index 50407a7ed7..2f1d3324b2 100644
--- a/src/openforms/forms/tests/test_api_form_plugin_options.py
+++ b/src/openforms/forms/tests/test_api_form_plugin_options.py
@@ -173,10 +173,16 @@ def test_overwrite_only_registration_email_subject_templates(self):
         response = self.client.patch(
             url,
             data={
-                "registration_backend_options": {
-                    "to_emails": ["test@test.nl"],
-                    "email_subject": "Custom subject",
-                }
+                "registration_backends": [
+                    {
+                        "key": "fst",
+                        "backend": "email",
+                        "options": {
+                            "to_emails": ["test@test.nl"],
+                            "email_subject": "Custom subject",
+                        },
+                    }
+                ]
             },
         )
 
@@ -205,26 +211,33 @@ def test_overwrite_both_registration_email_html_and_text_templates(self):
         response = self.client.patch(
             url,
             data={
-                "registration_backend_options": {
-                    "to_emails": ["test@test.nl"],
-                    "email_content_template_html": "Custom HTML template",
-                    "email_content_template_text": "Custom text template",
-                }
+                "registration_backends": [
+                    {
+                        "backend": "email",
+                        "options": {
+                            "to_emails": ["test@test.nl"],
+                            "email_content_template_html": "Custom HTML template",
+                            "email_content_template_text": "Custom text template",
+                        },
+                    }
+                ]
             },
         )
 
         self.assertEqual(response.status_code, 200)
 
         data = response.json()
+        self.assertEqual(len(data["registrationBackends"]), 1)
+        backend = data["registrationBackends"][0]
 
-        self.assertNotIn("emailSubject", data["registrationBackendOptions"])
-        self.assertNotIn("paymentSubject", data["registrationBackendOptions"])
+        self.assertNotIn("emailSubject", backend["options"])
+        self.assertNotIn("paymentSubject", backend["options"])
         self.assertEqual(
-            data["registrationBackendOptions"]["emailContentTemplateHtml"],
+            backend["options"]["emailContentTemplateHtml"],
             "Custom HTML template",
         )
         self.assertEqual(
-            data["registrationBackendOptions"]["emailContentTemplateText"],
+            backend["options"]["emailContentTemplateText"],
             "Custom text template",
         )
 
@@ -242,10 +255,15 @@ def test_cannot_overwrite_only_registration_email_html_template(self):
         response = self.client.patch(
             url,
             data={
-                "registration_backend_options": {
-                    "to_emails": ["test@test.nl"],
-                    "email_content_template_html": "Custom HTML template",
-                },
+                "registration_backends": [
+                    {
+                        "backend": "email",
+                        "options": {
+                            "to_emails": ["test@test.nl"],
+                            "email_content_template_html": "Custom HTML template",
+                        },
+                    }
+                ],
             },
         )
 
diff --git a/src/openforms/forms/tests/test_copy.py b/src/openforms/forms/tests/test_copy.py
index 3f5be01f15..a79e47b948 100644
--- a/src/openforms/forms/tests/test_copy.py
+++ b/src/openforms/forms/tests/test_copy.py
@@ -33,7 +33,10 @@ def test_form_copy_with_reusable_definition(self):
         self.assertNotEqual(copied_form.pk, form.pk)
         self.assertNotEqual(copied_form.uuid, str(form.uuid))
         self.assertEqual(copied_form.active, form.active)
-        self.assertEqual(copied_form.registration_backend, form.registration_backend)
+        self.assertEqual(
+            copied_form.registration_backends.count(),
+            form.registration_backends.count(),
+        )
         self.assertEqual(copied_form.name, _("{name} (copy)").format(name=form.name))
         self.assertIsNone(copied_form.product)
         self.assertEqual(copied_form.slug, _("{slug}-copy").format(slug=form.slug))
diff --git a/src/openforms/forms/tests/test_import_export.py b/src/openforms/forms/tests/test_import_export.py
index 6940f67dee..54552ea25a 100644
--- a/src/openforms/forms/tests/test_import_export.py
+++ b/src/openforms/forms/tests/test_import_export.py
@@ -281,10 +281,9 @@ def test_import(self):
         self.assertNotEqual(imported_form.pk, form_pk)
         self.assertNotEqual(imported_form.uuid, str(form.uuid))
         self.assertEqual(imported_form.active, False)
-        self.assertEqual(imported_form.registration_backend, form.registration_backend)
         self.assertEqual(
-            imported_form.registration_backend_options,
-            form.registration_backend_options,
+            imported_form.registration_backends.count(),
+            form.registration_backends.count(),
         )
         self.assertEqual(imported_form.name, form.name)
         self.assertIsNone(imported_form.product)
@@ -410,7 +409,10 @@ def test_import_form_definition_uuid_already_exists_configuration_duplicate(self
         self.assertNotEqual(imported_form.pk, form_pk)
         self.assertNotEqual(imported_form.uuid, form.uuid)
         self.assertEqual(imported_form.active, False)
-        self.assertEqual(imported_form.registration_backend, form.registration_backend)
+        self.assertEqual(
+            imported_form.registration_backends.count(),
+            form.registration_backends.count(),
+        )
         self.assertEqual(imported_form.name, form.name)
         self.assertEqual(imported_form.internal_name, form.internal_name)
         self.assertIsNone(imported_form.product)
@@ -477,7 +479,10 @@ def test_import_form_definition_uuid_already_exists_configuration_different(self
         self.assertNotEqual(imported_form.pk, form_pk)
         self.assertNotEqual(imported_form.uuid, form.uuid)
         self.assertEqual(imported_form.active, False)
-        self.assertEqual(imported_form.registration_backend, form.registration_backend)
+        self.assertEqual(
+            imported_form.registration_backends.count(),
+            form.registration_backends.count(),
+        )
         self.assertEqual(imported_form.name, form.name)
         self.assertEqual(imported_form.internal_name, form.internal_name)
         self.assertIsNone(imported_form.product)
diff --git a/src/openforms/forms/tests/test_serializers.py b/src/openforms/forms/tests/test_serializers.py
index c7dbc81741..d77f864a4b 100644
--- a/src/openforms/forms/tests/test_serializers.py
+++ b/src/openforms/forms/tests/test_serializers.py
@@ -19,8 +19,6 @@
     FormStepFactory,
     FormVariableFactory,
 )
-from openforms.registrations.base import BasePlugin as BaseRegistrationPlugin
-from openforms.registrations.registry import Registry as RegistrationPluginRegistry
 from openforms.tests.search_strategies import json_primitives
 from openforms.variables.constants import FormVariableDataTypes, FormVariableSources
 
@@ -270,9 +268,6 @@ def test_patching_registrations_deleting_the_first(self):
         )
         context = {"request": None}
         data = FormSerializer(context=context).to_representation(form)
-        # remove v2 data
-        del data["registration_backend"]
-        del data["registration_backend_options"]
 
         # delete the first line
         assert data["registration_backends"][0]["key"] == "backend1"
@@ -338,84 +333,3 @@ def test_patching_registrations_with_a_booboo(self):
         self.assertEqual(backend2.name, "#2")
         self.assertEqual(backend2.backend, "email")
         self.assertEqual(backend2.options["to_emails"], ["me@example.com"])
-
-    def test_patching_registration_passing_none_options(self):
-        # deprecated case
-        context = {"request": None}
-        data = FormSerializer(context=context).to_representation(
-            instance=FormFactory.create(slug="unicorn-slug")
-        )
-        # not a v3 call
-        del data["registration_backends"]
-        # options v2 are nullable
-        data["registration_backend"] = "nullable-unicorn"
-        data["registration_backend_options"] = None
-        data["slug"] = "another-slug"
-
-        mock_register = RegistrationPluginRegistry()
-
-        @mock_register("nullable-unicorn")
-        class UnicornPlugin(BaseRegistrationPlugin):
-            # This doesn't pass registry.check_plugin
-            # configuration_options = None
-
-            def register_submission(self, *args, **kwargs):
-                pass
-
-        # this
-        # UnicornPlugin.configuration_options.allow_null = True
-        # still raises in FormSerializer.validate_backend_options:
-        # ValidationError({'non_field_errors': [ErrorDetail(string='No data provided', code='null')]})
-
-        # In theory, a 3rd party could do
-        UnicornPlugin.configuration_options = None
-
-        with patch(f"{FormSerializer.__module__}.registration_register", mock_register):
-            serializer = FormSerializer(context=context, data=data)
-            self.assertTrue(serializer.is_valid())
-            form = serializer.save()
-
-        backends = list(form.registration_backends.all())
-        self.assertEqual(len(backends), 1)
-        self.assertEqual(backends[0].backend, "nullable-unicorn")
-        self.assertFalse(backends[0].options)
-
-    def test_patching_registrations_backend(self):
-        # testing v2 patching
-        form = FormFactory.create()
-        FormRegistrationBackendFactory.create(form=form, backend="demo-failing")
-        context = {"request": None}
-
-        serializer = FormSerializer(
-            instance=form,
-            context=context,
-            data={"registration_backend": "demo"},
-            partial=True,
-        )
-        self.assertTrue(serializer.is_valid())
-        serializer.save()
-        form.refresh_from_db()
-
-        self.assertEqual(form.registration_backends.count(), 1)
-        backend = form.registration_backends.first()
-        self.assertEqual(backend.backend, "demo")
-
-    def test_patching_registrations_backend_with_new_instance(self):
-        # testing v2 patching
-        form = FormFactory.create()
-        context = {"request": None}
-
-        serializer = FormSerializer(
-            instance=form,
-            context=context,
-            data={"registration_backend": "demo", "registration_backend_options": {}},
-            partial=True,
-        )
-
-        self.assertTrue(serializer.is_valid(raise_exception=True))
-        serializer.save()
-        form.refresh_from_db()
-
-        self.assertEqual(form.registration_backends.count(), 1)
-        backend = form.registration_backends.first()
-        self.assertEqual(backend.backend, "demo")
diff --git a/src/openforms/registrations/contrib/camunda/tests/test_backend_options.py b/src/openforms/registrations/contrib/camunda/tests/test_backend_options.py
index 2f81643065..55db5f6e26 100644
--- a/src/openforms/registrations/contrib/camunda/tests/test_backend_options.py
+++ b/src/openforms/registrations/contrib/camunda/tests/test_backend_options.py
@@ -55,9 +55,6 @@ def test_happy_flow(self):
         """
         self.maxDiff = None
         detail_response = self.client.get(self.endpoint).json()
-        # remove v2 attributes
-        del detail_response["registrationBackend"]
-        del detail_response["registrationBackendOptions"]
 
         data = {
             **detail_response,
@@ -253,26 +250,32 @@ def test_process_vars_incomplete_data(self):
         ]
         expected_errors = [
             {
-                "registrationBackendOptions.processVariables.0.enabled": "required",
-                "registrationBackendOptions.processVariables.0.componentKey": "required",
+                "registrationBackends.0.options.processVariables.0.enabled": "required",
+                "registrationBackends.0.options.processVariables.0.componentKey": "required",
             },
             {
-                "registrationBackendOptions.processVariables": "null",
+                "registrationBackends.0.options.processVariables": "null",
             },
             {
-                "registrationBackendOptions.processVariables.0.componentKey": "blank",
+                "registrationBackends.0.options.processVariables.0.componentKey": "blank",
             },
         ]
 
         for invalid_var, expected_error_codes in zip(invalid_vars, expected_errors):
             with self.subTest(invalid_var=invalid_var):
                 data = {
-                    "registrationBackendOptions": {
-                        "processDefinition": "invoice",
-                        "processDefinitionVersion": None,
-                        "processVariables": [invalid_var],
-                        "complexProcessVariables": [],
-                    },
+                    "registrationBackends": [
+                        {
+                            "backend": "camunda",
+                            "key": "test1",
+                            "options": {
+                                "processDefinition": "invoice",
+                                "processDefinitionVersion": None,
+                                "processVariables": [invalid_var],
+                                "complexProcessVariables": [],
+                            },
+                        }
+                    ]
                 }
 
                 response = self.client.patch(self.endpoint, data)
@@ -295,37 +298,43 @@ def test_complex_process_vars_incomplete_data(self):
         ]
         expected_errors = [
             {
-                "registrationBackendOptions.complexProcessVariables.0.enabled": "required",
-                "registrationBackendOptions.complexProcessVariables.0.alias": "required",
-                "registrationBackendOptions.complexProcessVariables.0.type": "required",
+                "registrationBackends.0.options.complexProcessVariables.0.enabled": "required",
+                "registrationBackends.0.options.complexProcessVariables.0.alias": "required",
+                "registrationBackends.0.options.complexProcessVariables.0.type": "required",
             },
             {
-                "registrationBackendOptions.complexProcessVariables": "null",
+                "registrationBackends.0.options.complexProcessVariables": "null",
             },
             {
-                "registrationBackendOptions.complexProcessVariables.0.alias": "blank",
-                "registrationBackendOptions.complexProcessVariables.0.type": "required",
+                "registrationBackends.0.options.complexProcessVariables.0.alias": "blank",
+                "registrationBackends.0.options.complexProcessVariables.0.type": "required",
             },
             {
-                "registrationBackendOptions.complexProcessVariables.0.type": "invalid_choice",
+                "registrationBackends.0.options.complexProcessVariables.0.type": "invalid_choice",
             },
             {
-                "registrationBackendOptions.complexProcessVariables.0.definition": "null",
+                "registrationBackends.0.options.complexProcessVariables.0.definition": "null",
             },
             {
-                "registrationBackendOptions.complexProcessVariables.0.definition": "not_a_dict",
+                "registrationBackends.0.options.complexProcessVariables.0.definition": "not_a_dict",
             },
         ]
 
         for invalid_var, expected_error_codes in zip(invalid_vars, expected_errors):
             with self.subTest(invalid_var=invalid_var):
                 data = {
-                    "registrationBackendOptions": {
-                        "processDefinition": "invoice",
-                        "processDefinitionVersion": None,
-                        "processVariables": [],
-                        "complexProcessVariables": [invalid_var],
-                    },
+                    "registrationBackends": [
+                        {
+                            "backend": "camunda",
+                            "key": "test1",
+                            "options": {
+                                "processDefinition": "invoice",
+                                "processDefinitionVersion": None,
+                                "processVariables": [],
+                                "complexProcessVariables": [invalid_var],
+                            },
+                        }
+                    ]
                 }
 
                 response = self.client.patch(self.endpoint, data)
diff --git a/src/openforms/submissions/admin.py b/src/openforms/submissions/admin.py
index 5f67dc9800..6160856886 100644
--- a/src/openforms/submissions/admin.py
+++ b/src/openforms/submissions/admin.py
@@ -361,7 +361,7 @@ def successfully_processed(self, obj) -> bool | None:
 
     @admin.display(description=_("Registration backend"))
     def get_registration_backend(self, obj):
-        return obj.form.registration_backend or "-"
+        return backend if (backend := obj.form.registration_backends.first()) else "-"
 
     @admin.display(description=_("Appointment status"))
     def get_appointment_status(self, obj):