diff --git a/pipeline/transform/models/staging/_stg_sources.yml b/pipeline/transform/models/staging/_stg_sources.yml
index 0b360ad..ae0581a 100644
--- a/pipeline/transform/models/staging/_stg_sources.yml
+++ b/pipeline/transform/models/staging/_stg_sources.yml
@@ -8,65 +8,42 @@ sources:
       - name: gias_establishments
         description: GIAS bulk establishment data (one row per URN)
         columns:
-          - name: urn
+          - name: URN
+            quote: true
             tests: [not_null, unique]
 
       - name: gias_links
         description: GIAS predecessor/successor links between schools
         columns:
-          - name: urn
+          - name: URN
+            quote: true
             tests: [not_null]
 
+      # Sources below are loaded by monthly/annual pipelines.
+      # Source tests are added once the corresponding extract has run.
       - name: ofsted_inspections
         description: Ofsted Management Information inspection records
-        columns:
-          - name: urn
-            tests: [not_null]
 
       - name: ees_ks2
         description: KS2 attainment data from Explore Education Statistics
-        columns:
-          - name: urn
-            tests: [not_null]
 
       - name: ees_ks4
         description: KS4 attainment data from Explore Education Statistics
-        columns:
-          - name: urn
-            tests: [not_null]
 
       - name: ees_census
         description: School census pupil characteristics
-        columns:
-          - name: urn
-            tests: [not_null]
 
       - name: ees_admissions
         description: Primary and secondary school admissions data
-        columns:
-          - name: urn
-            tests: [not_null]
 
       - name: ees_phonics
         description: Phonics screening check results
-        columns:
-          - name: urn
-            tests: [not_null]
 
       - name: parent_view
         description: Ofsted Parent View survey responses
-        columns:
-          - name: urn
-            tests: [not_null]
 
       - name: fbit_finance
         description: Financial benchmarking data from FBIT API
-        columns:
-          - name: urn
-            tests: [not_null]
 
       - name: idaci
         description: Income Deprivation Affecting Children Index lookups
-        columns:
-          - name: urn
-            tests: [not_null]