diff --git a/repositories/condition/property_uprn_lookup.py b/repositories/condition/property_uprn_lookup.py
index 0c8082675..cf2b2a344 100644
--- a/repositories/condition/property_uprn_lookup.py
+++ b/repositories/condition/property_uprn_lookup.py
@@ -1,4 +1,4 @@
-from typing import Dict
+from typing import Dict, List
 
 from repositories.condition.property_reference_reader import PropertyReferenceReader
 from repositories.condition.uprn_lookup import UprnLookup
@@ -21,3 +21,8 @@ class PropertyUprnLookup(UprnLookup):
             for ref in references
             if ref.landlord_property_id is not None and ref.uprn is not None
         }
+
+    def null_uprn_references(self) -> List[str]:
+        """Landlord references present in the portfolio whose UPRN is null —
+        surfaced so a load can report them (none expected; ADR-0064)."""
+        raise NotImplementedError
diff --git a/tests/condition/lookups/test_property_uprn_lookup.py b/tests/condition/lookups/test_property_uprn_lookup.py
index f303b55f1..265957b59 100644
--- a/tests/condition/lookups/test_property_uprn_lookup.py
+++ b/tests/condition/lookups/test_property_uprn_lookup.py
@@ -30,3 +30,20 @@ def test_property_uprn_lookup_excludes_rows_with_no_uprn():
 
     # Assert
     assert mapping == {"443": 100093305101}
+
+
+def test_property_uprn_lookup_reports_references_with_null_uprn():
+    # Arrange
+    reader = FakePropertyReferenceReader(
+        [
+            PropertyReference(landlord_property_id="443", uprn=100093305101),
+            PropertyReference(landlord_property_id="999", uprn=None),
+        ]
+    )
+    lookup = PropertyUprnLookup(reader, portfolio_id=824)
+
+    # Act
+    null_references = lookup.null_uprn_references()
+
+    # Assert
+    assert null_references == ["999"]