diff --git a/registrations/serializers.py b/registrations/serializers.py
index 59a4aa3cd..5e098720c 100644
--- a/registrations/serializers.py
+++ b/registrations/serializers.py
@@ -116,26 +116,21 @@ def validate(self, data):
 
         falsy_values = ("", None)
 
+        # Validate mandatory fields
         for field in registration.mandatory_fields:
-            if self.instance and field not in data.keys():
-                # Use existing value if field is missing in the payload
-                val = getattr(self.instance, field)
-            else:
-                val = data.get(field)
-
-            if val in falsy_values:
+            # Don't validate field if request method is PATCH and field is missing from the payload
+            if self.partial and field not in data.keys():
+                continue
+            elif data.get(field) in falsy_values:
                 errors[field] = _("This field must be specified.")
 
+        # Validate date_of_birth if audience_min_age or registration.audience_max_age is defined
+        # Don't validate date_of_birth if request method is PATCH and field is missing from the payload
         if (
             registration.audience_min_age not in falsy_values
             or registration.audience_max_age not in falsy_values
-        ):
-            if self.instance and "date_of_birth" not in data.keys():
-                # Use existing value if date_of_birth is missing in the payload
-                date_of_birth = self.instance.date_of_birth
-
-            else:
-                date_of_birth = data.get("date_of_birth")
+        ) and not (self.partial and "date_of_birth" not in data.keys()):
+            date_of_birth = data.get("date_of_birth")
 
             if date_of_birth in falsy_values:
                 errors["date_of_birth"] = _("This field must be specified.")
diff --git a/registrations/tests/test_signup_patch.py b/registrations/tests/test_signup_patch.py
new file mode 100644
index 000000000..62d698082
--- /dev/null
+++ b/registrations/tests/test_signup_patch.py
@@ -0,0 +1,50 @@
+import pytest
+from freezegun import freeze_time
+from rest_framework import status
+
+from events.tests.utils import versioned_reverse as reverse
+from registrations.models import MandatoryFields, SignUp
+
+# === util methods ===
+
+
+def patch_signup(api_client, signup_pk, signup_data):
+    signup_url = reverse(
+        "signup-detail",
+        kwargs={"pk": signup_pk},
+    )
+
+    response = api_client.patch(signup_url, signup_data, format="json")
+    return response
+
+
+def assert_patch_signup(api_client, signup_pk, signup_data):
+    response = patch_signup(api_client, signup_pk, signup_data)
+
+    assert response.status_code == status.HTTP_200_OK
+    assert response.data["id"] == signup_pk
+
+    return response
+
+
+@freeze_time("2023-03-14 03:30:00+02:00")
+@pytest.mark.django_db
+def test__patch_presence_status_of_signup(api_client, registration, signup, user):
+    registration.audience_min_age = 10
+    registration.mandatory_fields = [
+        MandatoryFields.PHONE_NUMBER,
+        MandatoryFields.STREET_ADDRESS,
+    ]
+    registration.save()
+    signup.date_of_birth = "2011-01-01"
+    signup.phone_number = "0441234567"
+    signup.street_address = "Street address"
+    signup.save()
+    api_client.force_authenticate(user)
+
+    signup_data = {
+        "presence_status": SignUp.PresenceStatus.PRESENT,
+    }
+
+    response = assert_patch_signup(api_client, signup.id, signup_data)
+    assert response.data["presence_status"] == SignUp.PresenceStatus.PRESENT
diff --git a/registrations/tests/test_signup_put.py b/registrations/tests/test_signup_put.py
index 9cb812401..f5855e5b2 100644
--- a/registrations/tests/test_signup_put.py
+++ b/registrations/tests/test_signup_put.py
@@ -3,7 +3,7 @@
 from rest_framework import status
 
 from events.tests.utils import versioned_reverse as reverse
-from registrations.models import MandatoryFields, SignUp
+from registrations.models import SignUp
 
 # === util methods ===
 
@@ -54,30 +54,6 @@ def test__update_signup(user_api_client, registration, signup, user):
     assert db_signup.last_modified_by_id == user.id
 
 
-@freeze_time("2023-03-14 03:30:00+02:00")
-@pytest.mark.django_db
-def test__update_presence_status_of_signup(api_client, registration, signup, user):
-    registration.audience_min_age = 10
-    registration.mandatory_fields = [
-        MandatoryFields.PHONE_NUMBER,
-        MandatoryFields.STREET_ADDRESS,
-    ]
-    registration.save()
-    signup.date_of_birth = "2011-01-01"
-    signup.phone_number = "0441234567"
-    signup.street_address = "Street address"
-    signup.save()
-    api_client.force_authenticate(user)
-
-    signup_data = {
-        "registration": registration.id,
-        "presence_status": SignUp.PresenceStatus.PRESENT,
-    }
-
-    response = assert_update_signup(api_client, signup.id, signup_data)
-    assert response.data["presence_status"] == SignUp.PresenceStatus.PRESENT
-
-
 @freeze_time("2023-03-14 03:30:00+02:00")
 @pytest.mark.django_db
 def test__created_regular_user_can_update_signup(