diff --git a/app/models/case_log.rb b/app/models/case_log.rb
index 5ad7e515e..16c08bc0b 100644
--- a/app/models/case_log.rb
+++ b/app/models/case_log.rb
@@ -38,6 +38,12 @@ class CaseLogValidator < ActiveModel::Validator
       record.errors.add :other_reason_for_leaving_last_settled_home, "The other reason must not be provided if the reason for leaving settled home was not other"
     end
   end
+  
+  def validate_reason_for_leaving_last_settled_home(record)
+    if record.reason_for_leaving_last_settled_home == "Do not know" && record.benefit_cap_spare_room_subsidy != "Do not know"
+      record.errors.add :benefit_cap_spare_room_subsidy, "must be do not know if tenant’s main reason for leaving is do not know"
+    end
+  end
 
   def validate(record)
     # If we've come from the form UI we only want to validate the specific fields
diff --git a/config/forms/2021_2022.json b/config/forms/2021_2022.json
index 47378e9f0..1d2d72b57 100644
--- a/config/forms/2021_2022.json
+++ b/config/forms/2021_2022.json
@@ -612,7 +612,7 @@
               "header": "Leaving their last settled home",
               "description": "",
               "questions": {
-                "last_settled_home": {
+                "reason_for_leaving_last_settled_home": {
                   "header": "What is the tenant’s main reason for leaving?",
                   "hint_text": "",
                   "type": "radio",
diff --git a/db/schema.rb b/db/schema.rb
index 03a612ecd..42b14adc9 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -130,8 +130,8 @@ ActiveRecord::Schema.define(version: 2021_10_15_090040) do
     t.boolean "reasonable_preference_reason_medical_grounds"
     t.boolean "reasonable_preference_reason_avoid_hardship"
     t.boolean "reasonable_preference_reason_do_not_know"
-    t.datetime "discarded_at"
     t.integer "property_number_of_times_relet"
+    t.datetime "discarded_at"
     t.index ["discarded_at"], name: "index_case_logs_on_discarded_at"
   end