diff --git a/app/controllers/users/dossiers_controller.rb b/app/controllers/users/dossiers_controller.rb
index f4c0e76a3..005c62c8e 100644
--- a/app/controllers/users/dossiers_controller.rb
+++ b/app/controllers/users/dossiers_controller.rb
@@ -128,7 +128,7 @@ module Users
       @dossier = dossier
       @no_description = true
 
-      if @dossier.individual.update(individual_params)
+      if @dossier.update(dossier_params)
         @dossier.update!(autorisation_donnees: true, identity_updated_at: Time.zone.now)
         flash.notice = t('.identity_saved')
 
@@ -589,8 +589,8 @@ module Users
       render :siret
     end
 
-    def individual_params
-      params.require(:individual).permit(:gender, :nom, :prenom, :birthdate)
+    def dossier_params
+      params.require(:dossier).permit(:for_tiers, :mandataire_first_name, :mandataire_last_name, individual_attributes: [:gender, :nom, :prenom, :birthdate, :email, :notification_method])
     end
 
     def siret_params
diff --git a/app/javascript/controllers/for_tiers_controller.ts b/app/javascript/controllers/for_tiers_controller.ts
new file mode 100644
index 000000000..7aa955da0
--- /dev/null
+++ b/app/javascript/controllers/for_tiers_controller.ts
@@ -0,0 +1,93 @@
+import { ApplicationController } from './application_controller';
+
+export class ForTiersController extends ApplicationController {
+  static targets = [
+    'mandataireFirstName',
+    'mandataireLastName',
+    'forTiers',
+    'mandataireBlock',
+    'beneficiaireNotificationBlock',
+    'email',
+    'notificationMethod',
+    'mandataireTitle',
+    'beneficiaireTitle',
+    'emailInput'
+  ];
+
+  declare mandataireFirstNameTarget: HTMLInputElement;
+  declare mandataireLastNameTarget: HTMLInputElement;
+  declare forTiersTargets: NodeListOf<HTMLInputElement>;
+  declare mandataireBlockTarget: HTMLElement;
+  declare beneficiaireNotificationBlockTarget: HTMLElement;
+  declare notificationMethodTargets: NodeListOf<HTMLInputElement>;
+  declare emailTarget: HTMLInputElement;
+  declare mandataireTitleTarget: HTMLElement;
+  declare beneficiaireTitleTarget: HTMLElement;
+  declare emailInput: HTMLInputElement;
+
+  connect() {
+    const emailInputElement = this.emailTarget.querySelector('input');
+    if (emailInputElement) {
+      this.emailInput = emailInputElement;
+    }
+    this.toggleFieldRequirements();
+    this.addAllEventListeners();
+  }
+
+  addAllEventListeners() {
+    this.forTiersTargets.forEach((radio) => {
+      radio.addEventListener('change', () => this.toggleFieldRequirements());
+    });
+    this.notificationMethodTargets.forEach((radio) => {
+      radio.addEventListener('change', () => this.toggleEmailInput());
+    });
+  }
+
+  toggleFieldRequirements() {
+    const forTiersSelected = this.isForTiersSelected();
+    this.toggleDisplay(this.mandataireBlockTarget, forTiersSelected);
+    this.toggleDisplay(
+      this.beneficiaireNotificationBlockTarget,
+      forTiersSelected
+    );
+    this.mandataireFirstNameTarget.required = forTiersSelected;
+    this.mandataireLastNameTarget.required = forTiersSelected;
+    this.mandataireTitleTarget.classList.toggle('hidden', forTiersSelected);
+    this.beneficiaireTitleTarget.classList.toggle('hidden', !forTiersSelected);
+    this.notificationMethodTargets.forEach((radio) => {
+      radio.required = forTiersSelected;
+    });
+
+    this.toggleEmailInput();
+  }
+
+  isForTiersSelected() {
+    return Array.from(this.forTiersTargets).some(
+      (radio) => radio.checked && radio.value === 'true'
+    );
+  }
+
+  toggleDisplay(element: HTMLElement, shouldDisplay: boolean) {
+    element.classList.toggle('hidden', !shouldDisplay);
+  }
+  toggleEmailInput() {
+    const isEmailSelected = this.isEmailSelected();
+    const forTiersSelected = this.isForTiersSelected();
+
+    if (this.emailInput) {
+      this.emailInput.required = forTiersSelected && isEmailSelected;
+
+      if (!isEmailSelected) {
+        this.emailInput.value = '';
+      }
+
+      this.toggleDisplay(this.emailTarget, forTiersSelected && isEmailSelected);
+    }
+  }
+
+  isEmailSelected() {
+    return Array.from(this.notificationMethodTargets).some(
+      (radio) => radio.value === 'email' && radio.checked
+    );
+  }
+}