diff --git a/app/models/sales_log.rb b/app/models/sales_log.rb
index c7fe68bca..ca83a9cf0 100644
--- a/app/models/sales_log.rb
+++ b/app/models/sales_log.rb
@@ -78,6 +78,7 @@ class SalesLog < Log
   def dynamically_not_required
     not_required = []
     not_required << "proplen" if proplen_optional?
+    not_required << "mortlen" if mortlen_optional?
 
     not_required |= %w[address_line2 county postcode_full] if saledate && saledate.year >= 2023
 
@@ -90,6 +91,12 @@ class SalesLog < Log
     collection_start_year < 2023
   end
 
+  def mortlen_optional?
+    return false unless collection_start_year
+
+    collection_start_year < 2023
+  end
+
   def not_started?
     status == "not_started"
   end
diff --git a/spec/models/sales_log_spec.rb b/spec/models/sales_log_spec.rb
index 7f6c74fc4..a6fc002d5 100644
--- a/spec/models/sales_log_spec.rb
+++ b/spec/models/sales_log_spec.rb
@@ -60,6 +60,7 @@ RSpec.describe SalesLog, type: :model do
           monthly_charges_value_check
           old_persons_shared_ownership_value_check
           proplen
+          mortlen
         ])
       end
     end