diff --git a/repositories/condition/property_uprn_lookup.py b/repositories/condition/property_uprn_lookup.py
index b9c8e4e2a..0c8082675 100644
--- a/repositories/condition/property_uprn_lookup.py
+++ b/repositories/condition/property_uprn_lookup.py
@@ -15,4 +15,9 @@ class PropertyUprnLookup(UprnLookup):
         self._portfolio_id = portfolio_id
 
     def get_property_ref_to_uprn_lookup(self) -> Dict[str, int]:
-        raise NotImplementedError
+        references = self._reader.references_for_portfolio(self._portfolio_id)
+        return {
+            ref.landlord_property_id: ref.uprn
+            for ref in references
+            if ref.landlord_property_id is not None and ref.uprn is not None
+        }