diff --git a/app/models/question/selection.rb b/app/models/question/selection.rb
index a67f6ae89..df2eebf51 100644
--- a/app/models/question/selection.rb
+++ b/app/models/question/selection.rb
@@ -104,21 +104,6 @@ def none_of_the_above_question_text
       "#{none_of_the_above_question.question_text} #{I18n.t('page.optional')}"
     end
 
-    def selection=(value)
-      # TODO: This setter can be removed after 15/06/2026
-      if allow_multiple_answers?
-        if value.include?(I18n.t("page.none_of_the_above", locale: :en)) || value.include?(I18n.t("page.none_of_the_above", locale: :cy))
-          super([NONE_OF_THE_ABOVE_VALUE])
-          return
-        end
-      elsif value == I18n.t("page.none_of_the_above", locale: :en) || value == I18n.t("page.none_of_the_above", locale: :cy)
-        super(NONE_OF_THE_ABOVE_VALUE)
-        return
-      end
-
-      super(value)
-    end
-
   private
 
     def clear_none_of_the_above_answer_if_not_selected
diff --git a/spec/models/question/selection_spec.rb b/spec/models/question/selection_spec.rb
index 2a9eab273..664098c66 100644
--- a/spec/models/question/selection_spec.rb
+++ b/spec/models/question/selection_spec.rb
@@ -761,36 +761,4 @@
       end
     end
   end
-
-  describe "backwards compatibility for none of the above option" do
-    let(:is_optional) { true }
-
-    context "when the selection question is a checkbox" do
-      let(:only_one_option) { "false" }
-
-      it "sets the selection to ['none_of_the_above'] when attempting to set to the English localised translation" do
-        question.selection = [I18n.t("page.none_of_the_above")]
-        expect(question.selection).to eq([Question::Selection::NONE_OF_THE_ABOVE_VALUE])
-      end
-
-      it "sets the selection to ['none_of_the_above'] when attempting to set to the Welsh localised translation" do
-        question.selection = [I18n.t("page.none_of_the_above", locale: :cy)]
-        expect(question.selection).to eq([Question::Selection::NONE_OF_THE_ABOVE_VALUE])
-      end
-    end
-
-    context "when the selection question is a radio button" do
-      let(:only_one_option) { "true" }
-
-      it "sets the selection to 'none_of_the_above' when attempting to set to the English localised translation" do
-        question.selection = I18n.t("page.none_of_the_above")
-        expect(question.selection).to eq(Question::Selection::NONE_OF_THE_ABOVE_VALUE)
-      end
-
-      it "sets the selection to 'none_of_the_above' when attempting to set to the Welsh localised translation" do
-        question.selection = I18n.t("page.none_of_the_above", locale: :cy)
-        expect(question.selection).to eq(Question::Selection::NONE_OF_THE_ABOVE_VALUE)
-      end
-    end
-  end
 end