diff --git a/app/services/location_service.py b/app/services/location_service.py
index d7402c3..d96fc6e 100644
--- a/app/services/location_service.py
+++ b/app/services/location_service.py
@@ -35,6 +35,10 @@ def _is_transit_location(location_code: str) -> bool:
     return location_code.startswith("TRANS-")
 
 
+def _is_temp_storage_location(location_code: str) -> bool:
+    return location_code.startswith("B")
+
+
 def _erp_info_sql(db: Session) -> str:
     dialect_name = db.bind.dialect.name if db.bind is not None else ""
     if dialect_name == "postgresql":
@@ -74,7 +78,9 @@ def _query_paicha_no(db: Session, zongpai_no: str) -> str:
 
 
 def _query_paicha_items(db: Session, paicha_no: str) -> list[dict]:
-    rows = db.execute(text(_erp_paicha_items_sql(db)), {"paicha_no": paicha_no}).fetchall()
+    rows = db.execute(
+        text(_erp_paicha_items_sql(db)), {"paicha_no": paicha_no}
+    ).fetchall()
     return [
         {
             "zongpai_no": row[0],
@@ -90,6 +96,8 @@ def _location_status(location_code: str | None) -> str:
         return "not_shelved"
     if _is_transit_location(location_code):
         return "transferred"
+    if _is_temp_storage_location(location_code):
+        return "temp_stored"
     return "on_shelf"
 
 
@@ -111,18 +119,20 @@ def get_paicha_overview(db: Session, zongpai_no: str) -> dict:
     )
     location_map = {item.zongpai_no: item.location_code for item in locations}
 
-    status_order = {"on_shelf": 0, "transferred": 1, "not_shelved": 2}
+    status_order = {"on_shelf": 0, "temp_stored": 1, "transferred": 2, "not_shelved": 3}
     overview_items = []
     for item in erp_items:
         location_code = location_map.get(item["zongpai_no"])
         status = _location_status(location_code)
-        overview_items.append({
-            "zongpai_no": item["zongpai_no"],
-            "work_order_no": item["work_order_no"],
-            "quantity": item["quantity"],
-            "location_code": location_code,
-            "status": status,
-        })
+        overview_items.append(
+            {
+                "zongpai_no": item["zongpai_no"],
+                "work_order_no": item["work_order_no"],
+                "quantity": item["quantity"],
+                "location_code": location_code,
+                "status": status,
+            }
+        )
 
     overview_items.sort(
         key=lambda item: (
@@ -145,13 +155,19 @@ def register_location(db: Session, req: LocationRequest) -> FinishedGoodsLocatio
         .first()
     )
     if existing:
+        # Terminal state: transit location → any operation raises error
         if _is_transit_location(existing.location_code):
             raise AlreadyOffShelfError(
                 location_code=existing.location_code,
                 registered_at=existing.created_at.isoformat(),
             )
 
-        if _is_transit_location(req.location_code):
+        target_is_transit = _is_transit_location(req.location_code)
+        target_is_temp = _is_temp_storage_location(req.location_code)
+        current_is_temp = _is_temp_storage_location(existing.location_code)
+
+        # Allowed: target is transit (off-shelf) or normal→temp (shelf change)
+        if target_is_transit or (not current_is_temp and target_is_temp):
             previous_location = existing.location_code
             existing.location_code = req.location_code
             existing.created_at = datetime.now()