diff --git a/app/controllers/new_user/dossiers_controller.rb b/app/controllers/new_user/dossiers_controller.rb
index 2d1875cec..44b0faef4 100644
--- a/app/controllers/new_user/dossiers_controller.rb
+++ b/app/controllers/new_user/dossiers_controller.rb
@@ -101,11 +101,15 @@ module NewUser
 
     def ask_deletion
       dossier = current_user.dossiers.includes(:user, procedure: :administrateur).find(params[:id])
-      deleted_dossier = dossier.delete_and_keep_track
-      DossierMailer.notify_deletion_to_user(deleted_dossier, dossier.user.email).deliver_later
-      DossierMailer.notify_deletion_to_administration(deleted_dossier, dossier.procedure.administrateur.email).deliver_later
-      flash.notice = 'Votre dossier a bien été supprimé.'
-      redirect_to users_dossiers_path
+
+      if !dossier.instruction_commencee?
+        dossier.delete_and_keep_track
+        flash.notice = 'Votre dossier a bien été supprimé.'
+        redirect_to users_dossiers_path
+      else
+        flash.notice = "L'instruction de votre dossier a commencé, il n'est plus possible de supprimer votre dossier. Si vous souhaitez annuler l'instruction contactez votre administration par la messagerie de votre dossier."
+        redirect_to users_dossier_path(dossier)
+      end
     end
 
     private
diff --git a/app/helpers/dossier_helper.rb b/app/helpers/dossier_helper.rb
index bb90efa41..8e2bc2b35 100644
--- a/app/helpers/dossier_helper.rb
+++ b/app/helpers/dossier_helper.rb
@@ -14,14 +14,4 @@ module DossierHelper
       "highlighted"
     end
   end
-
-  def delete_dossier_confirm(dossier)
-    message = ["Vous vous apprêtez à supprimer votre dossier ainsi que les informations qu’il contient."]
-    if dossier.en_construction_ou_instruction?
-      message << "Nous vous rappelons que toute suppression entraine l’annulation de la démarche en cours."
-    end
-    message << "Confirmer la suppression ?"
-
-    message.join(" ")
-  end
 end
diff --git a/app/mailers/dossier_mailer.rb b/app/mailers/dossier_mailer.rb
index 96e2b46b0..03147e8b9 100644
--- a/app/mailers/dossier_mailer.rb
+++ b/app/mailers/dossier_mailer.rb
@@ -14,4 +14,11 @@ class DossierMailer < ApplicationMailer
 
     mail(to: to_email, subject: subject)
   end
+
+  def notify_unhide_to_user(dossier)
+    @dossier = dossier
+    subject = "Votre dossier n° #{@dossier.id} n'a pas pu être supprimé"
+
+    mail(to: dossier.user.email, subject: subject)
+  end
 end
diff --git a/app/models/dossier.rb b/app/models/dossier.rb
index 940116a3d..646aee849 100644
--- a/app/models/dossier.rb
+++ b/app/models/dossier.rb
@@ -44,6 +44,7 @@ class Dossier < ApplicationRecord
   scope :state_en_construction,                -> { where(state: 'en_construction') }
   scope :state_en_instruction,                 -> { where(state: 'en_instruction') }
   scope :state_en_construction_ou_instruction, -> { where(state: EN_CONSTRUCTION_OU_INSTRUCTION) }
+  scope :state_instruction_commencee,          -> { where(state: INSTRUCTION_COMMENCEE) }
   scope :state_termine,                        -> { where(state: TERMINE) }
 
   scope :archived,      -> { where(archived: true) }
@@ -126,6 +127,10 @@ class Dossier < ApplicationRecord
     TERMINE.include?(state)
   end
 
+  def instruction_commencee?
+    INSTRUCTION_COMMENCEE.include?(state)
+  end
+
   def cerfa_available?
     procedure.cerfa_flag? && cerfa.size != 0
   end
@@ -276,7 +281,8 @@ class Dossier < ApplicationRecord
     now = Time.now
     deleted_dossier = DeletedDossier.create!(dossier_id: id, procedure: procedure, state: state, deleted_at: now)
     update(hidden_at: now)
-    deleted_dossier
+    DossierMailer.notify_deletion_to_user(deleted_dossier, user.email).deliver_later
+    DossierMailer.notify_deletion_to_administration(deleted_dossier, procedure.administrateur.email).deliver_later
   end
 
   private
diff --git a/app/views/dossier_mailer/notify_unhide_to_user.html.haml b/app/views/dossier_mailer/notify_unhide_to_user.html.haml
new file mode 100644
index 000000000..6901a01e3
--- /dev/null
+++ b/app/views/dossier_mailer/notify_unhide_to_user.html.haml
@@ -0,0 +1,13 @@
+- content_for(:title, "Votre dossier n° #{@dossier.id} n'a pas pu être supprimé")
+
+%h1 Bonjour,
+
+%p
+  L'instruction de votre dossier n° #{@dossier.id} ayant commencé, il n'a pas pu être supprimé.
+  Le dossier a été rétabli dans votre tableau de bord.
+
+%p
+  Bonne journée,
+
+%p
+  L'équipe demarches-simplifiees.fr
diff --git a/app/views/layouts/left_panels/_left_panel_users_recapitulatifcontroller_show.html.haml b/app/views/layouts/left_panels/_left_panel_users_recapitulatifcontroller_show.html.haml
index 6c3499cd4..6f2031b6a 100644
--- a/app/views/layouts/left_panels/_left_panel_users_recapitulatifcontroller_show.html.haml
+++ b/app/views/layouts/left_panels/_left_panel_users_recapitulatifcontroller_show.html.haml
@@ -14,9 +14,9 @@
   .dossier-state= @facade.dossier.display_state
   .split-hr-left
 
-  - if current_user.owns?(@facade.dossier)
+  - if current_user.owns?(@facade.dossier) && !@facade.dossier.instruction_commencee?
     .text-center.mt-1
-      = link_to ask_deletion_dossier_path(@facade.dossier), method: :post, class: "btn btn-danger", data: { confirm: delete_dossier_confirm(@facade.dossier) } do
+      = link_to ask_deletion_dossier_path(@facade.dossier), method: :post, class: "btn btn-danger", data: { confirm: "Vous vous apprêtez à supprimer votre dossier ainsi que les informations qu’il contient. Nous vous rappelons que toute suppression entraine l’annulation de la démarche en cours. Confirmer la suppression ?" } do
         Supprimer définitivement
         %br
         ce dossier
diff --git a/lib/tasks/2018_06_13_unhide_dossiers.rake b/lib/tasks/2018_06_13_unhide_dossiers.rake
new file mode 100644
index 000000000..c5221fe74
--- /dev/null
+++ b/lib/tasks/2018_06_13_unhide_dossiers.rake
@@ -0,0 +1,11 @@
+namespace :'2018_06_13_unhide_dossiers' do
+  task run: :environment do
+    Dossier.unscoped.where.not(hidden_at: nil).state_instruction_commencee.each do |d|
+      if !d.procedure.nil? # ensure the procedure was not deleted by administrateur for testing
+        d.update(hidden_at: nil)
+        DeletedDossier.find_by(dossier_id: d.id)&.destroy
+        DossierMailer.notify_unhide_to_user(d).deliver_later
+      end
+    end
+  end
+end
diff --git a/spec/controllers/new_user/dossiers_controller_spec.rb b/spec/controllers/new_user/dossiers_controller_spec.rb
index 887d81beb..5be0295da 100644
--- a/spec/controllers/new_user/dossiers_controller_spec.rb
+++ b/spec/controllers/new_user/dossiers_controller_spec.rb
@@ -412,6 +412,20 @@ describe NewUser::DossiersController, type: :controller do
 
     subject { post :ask_deletion, params: { id: dossier.id } }
 
+    shared_examples_for "the dossier can not be deleted" do
+      it do
+        expect(DossierMailer).not_to receive(:notify_deletion_to_administration)
+        expect(DossierMailer).not_to receive(:notify_deletion_to_user)
+        subject
+      end
+
+      it do
+        subject
+        expect(Dossier.find_by(id: dossier.id)).not_to eq(nil)
+        expect(dossier.procedure.deleted_dossiers.count).to eq(0)
+      end
+    end
+
     context 'when dossier is owned by signed in user' do
       let(:dossier) { create(:dossier, user: user, autorisation_donnees: true) }
 
@@ -429,25 +443,22 @@ describe NewUser::DossiersController, type: :controller do
         expect(procedure.deleted_dossiers.count).to eq(1)
         expect(procedure.deleted_dossiers.first.dossier_id).to eq(dossier_id)
       end
+
       it { is_expected.to redirect_to(users_dossiers_path) }
+
+      context "and the instruction has started" do
+        let(:dossier) { create(:dossier, :en_instruction, user: user, autorisation_donnees: true) }
+
+        it_behaves_like "the dossier can not be deleted"
+        it { is_expected.to redirect_to(users_dossier_path(dossier)) }
+      end
     end
 
     context 'when dossier is not owned by signed in user' do
       let(:user2) { create(:user) }
       let(:dossier) { create(:dossier, user: user2, autorisation_donnees: true) }
 
-      it do
-        expect(DossierMailer).not_to receive(:notify_deletion_to_administration)
-        expect(DossierMailer).not_to receive(:notify_deletion_to_user)
-        subject
-      end
-
-      it do
-        subject
-        expect(Dossier.find_by(id: dossier.id)).not_to eq(nil)
-        expect(dossier.procedure.deleted_dossiers.count).to eq(0)
-      end
-
+      it_behaves_like "the dossier can not be deleted"
       it { is_expected.to redirect_to(root_path) }
     end
   end