diff --git a/applications/abri/abri_trigger_request.py b/applications/abri/abri_trigger_request.py
index 003fe47bb..50deed371 100644
--- a/applications/abri/abri_trigger_request.py
+++ b/applications/abri/abri_trigger_request.py
@@ -45,12 +45,15 @@ class AbriTriggerRequest(BaseModel):
     # OpenHousing's bookable resource for the survey; required by the log and
     # amend flows. Empty string is also rejected by Abri, so not allowed here
     third_party_surveyor_identifier: Optional[str] = None
+    # The Job Number OpenHousing returns on a successful log. Present means the
+    # job exists (amend/abandon); absent means it was never logged (or the
+    # reference was lost). Passed through, not required by any flow. A blank
+    # value carries no Job Number, so it is normalised to missing.
+    client_booking_reference: Optional[str] = None
 
-    @field_validator("third_party_surveyor_identifier")
+    @field_validator("third_party_surveyor_identifier", "client_booking_reference")
     @classmethod
-    def _blank_surveyor_identifier_is_missing(
-        cls, value: Optional[str]
-    ) -> Optional[str]:
+    def _blank_is_missing(cls, value: Optional[str]) -> Optional[str]:
         if value is not None and not value.strip():
             return None
         return value