diff --git a/app/models/dossier.rb b/app/models/dossier.rb
index 263609e78..ef4ad39b6 100644
--- a/app/models/dossier.rb
+++ b/app/models/dossier.rb
@@ -183,6 +183,16 @@ class Dossier < ApplicationRecord
     brouillon? || en_construction?
   end
 
+  def retention_end_date
+    if instruction_commencee?
+      en_instruction_at + procedure.duree_conservation_dossiers_dans_ds.months
+    end
+  end
+
+  def retention_expired?
+    instruction_commencee? && retention_end_date <= DateTime.now
+  end
+
   def text_summary
     if brouillon?
       parts = [
diff --git a/spec/models/dossier_spec.rb b/spec/models/dossier_spec.rb
index ea60ea3be..f2a1be974 100644
--- a/spec/models/dossier_spec.rb
+++ b/spec/models/dossier_spec.rb
@@ -1002,4 +1002,30 @@ describe Dossier do
       it { is_expected.to be false }
     end
   end
+
+  context "retention date" do
+    let(:procedure) { create(:procedure, duree_conservation_dossiers_dans_ds: 6) }
+    let(:uninstructed_dossier) { create(:dossier, :en_construction, procedure: procedure) }
+    let(:young_dossier) { create(:dossier, :en_instruction, en_instruction_at: DateTime.now, procedure: procedure) }
+    let(:just_expired_dossier) { create(:dossier, :en_instruction, en_instruction_at: 6.months.ago, procedure: procedure) }
+    let(:long_expired_dossier) { create(:dossier, :en_instruction, en_instruction_at: 1.year.ago, procedure: procedure) }
+    let(:modif_date) { DateTime.parse('01/01/2100') }
+
+    before { Timecop.freeze(modif_date) }
+    after { Timecop.return }
+
+    describe "#retention_end_date" do
+      it { expect(uninstructed_dossier.retention_end_date).to be_nil }
+      it { expect(young_dossier.retention_end_date).to eq(6.months.from_now) }
+      it { expect(just_expired_dossier.retention_end_date).to eq(DateTime.now) }
+      it { expect(long_expired_dossier.retention_end_date).to eq(6.months.ago) }
+    end
+
+    describe "#retention_expired?" do
+      it { expect(uninstructed_dossier).not_to be_retention_expired }
+      it { expect(young_dossier).not_to be_retention_expired }
+      it { expect(just_expired_dossier).to be_retention_expired }
+      it { expect(long_expired_dossier).to be_retention_expired }
+    end
+  end
 end