diff --git a/app/models/derived_variables/lettings_log_variables.rb b/app/models/derived_variables/lettings_log_variables.rb
index f584b6238e..1e2aab7901 100644
--- a/app/models/derived_variables/lettings_log_variables.rb
+++ b/app/models/derived_variables/lettings_log_variables.rb
@@ -72,6 +72,7 @@ def set_derived_fields!
       self.beds = 1
     end
 
+    clear_child_ecstat_for_age_changes!
     child_under_16_constraints!
 
     self.hhtype = household_type
@@ -243,6 +244,14 @@ def child_under_16_constraints!
     end
   end
 
+  def clear_child_ecstat_for_age_changes!
+    (2..8).each do |idx|
+      if public_send("age#{idx}_changed?") && self["ecstat#{idx}"] == 9
+        self["ecstat#{idx}"] = nil
+      end
+    end
+  end
+
   def household_type
     return unless totelder && totadult && totchild
 
diff --git a/app/models/derived_variables/sales_log_variables.rb b/app/models/derived_variables/sales_log_variables.rb
index ef4997283a..ff8cd49169 100644
--- a/app/models/derived_variables/sales_log_variables.rb
+++ b/app/models/derived_variables/sales_log_variables.rb
@@ -46,6 +46,7 @@ def set_derived_fields!
 
     if saledate && form.start_year_2024_or_later?
       self.soctenant = soctenant_from_prevten_values
+      clear_child_ecstat_for_age_changes!
       child_under_16_constraints!
     end
 
@@ -181,6 +182,15 @@ def child_under_16_constraints!
     end
   end
 
+  def clear_child_ecstat_for_age_changes!
+    start_index = joint_purchase? ? 3 : 2
+    (start_index..6).each do |idx|
+      if public_send("age#{idx}_changed?") && self["ecstat#{idx}"] == 9
+        self["ecstat#{idx}"] = nil
+      end
+    end
+  end
+
   def household_type
     return unless total_elder && total_adult && totchild
 
diff --git a/spec/models/lettings_log_derived_fields_spec.rb b/spec/models/lettings_log_derived_fields_spec.rb
index d315db51e1..e4edb194e1 100644
--- a/spec/models/lettings_log_derived_fields_spec.rb
+++ b/spec/models/lettings_log_derived_fields_spec.rb
@@ -1206,4 +1206,24 @@
       end
     end
   end
+
+  describe "#clear_child_ecstat_for_age_changes!" do
+    it "clears the working situation of a person that was previously a child under 16" do
+      log = create(:lettings_log, :completed, age2: 13)
+      log.age2 = 17
+      expect { log.set_derived_fields! }.to change(log, :ecstat2).from(9).to(nil)
+    end
+
+    it "does not clear the working situation of a person that had an age change but is still a child under 16" do
+      log = create(:lettings_log, :completed, age2: 13)
+      log.age2 = 15
+      expect { log.set_derived_fields! }.to not_change(log, :ecstat2)
+    end
+
+    it "does not clear the working situation of a person that had an age change but is still an adult" do
+      log = create(:lettings_log, :completed, age2: 45)
+      log.age2 = 46
+      expect { log.set_derived_fields! }.to not_change(log, :ecstat2)
+    end
+  end
 end
diff --git a/spec/models/sales_log_derived_fields_spec.rb b/spec/models/sales_log_derived_fields_spec.rb
index 8eda0c36f0..7827ce2820 100644
--- a/spec/models/sales_log_derived_fields_spec.rb
+++ b/spec/models/sales_log_derived_fields_spec.rb
@@ -78,6 +78,26 @@
       expect { log.set_derived_fields! }.to change(log, :mortgage).from(50_000).to(nil)
     end
 
+    describe "#clear_child_ecstat_for_age_changes!" do
+      it "clears the working situation of a person that was previously a child under 16" do
+        log = create(:sales_log, :completed, age3: 13, age4: 16, age5: 45)
+        log.age3 = 17
+        expect { log.set_derived_fields! }.to change(log, :ecstat3).from(9).to(nil)
+      end
+
+      it "does not clear the working situation of a person that had an age change but is still a child under 16" do
+        log = create(:sales_log, :completed, age3: 13, age4: 16, age5: 45)
+        log.age3 = 15
+        expect { log.set_derived_fields! }.to not_change(log, :ecstat3)
+      end
+
+      it "does not clear the working situation of a person that had an age change but is still an adult" do
+        log = create(:sales_log, :completed, age3: 13, age4: 16, age5: 45)
+        log.age5 = 46
+        expect { log.set_derived_fields! }.to not_change(log, :ecstat5)
+      end
+    end
+
     context "with a log that is not outright sales" do
       it "does not derive deposit when mortgage used is no" do
         log = build(:sales_log, :shared_ownership_setup_complete, value: 123_400, deposit: nil, mortgageused: 2)