diff --git a/thanasoft-back/app/Http/Requests/StoreInvoiceRequest.php b/thanasoft-back/app/Http/Requests/StoreInvoiceRequest.php
index 45f489c..2f5168d 100644
--- a/thanasoft-back/app/Http/Requests/StoreInvoiceRequest.php
+++ b/thanasoft-back/app/Http/Requests/StoreInvoiceRequest.php
@@ -22,7 +22,7 @@ class StoreInvoiceRequest extends FormRequest
     public function rules(): array
     {
         return [
-            'client_id' => 'required|exists:clients,id',
+            'client_id' => 'nullable|exists:clients,id',
             'group_id' => 'nullable|exists:client_groups,id',
             'source_quote_id' => 'nullable|exists:quotes,id',
             'status' => 'required|in:brouillon,emise,envoyee,partiellement_payee,payee,echue,annulee,avoir',
@@ -49,10 +49,31 @@ class StoreInvoiceRequest extends FormRequest
         ];
     }
 
+    public function withValidator($validator): void
+    {
+        $validator->after(function ($validator) {
+            $hasClient = filled($this->input('client_id'));
+            $hasGroup = filled($this->input('group_id'));
+
+            if (! $hasClient && ! $hasGroup) {
+                $message = 'Un client ou un groupe de clients est obligatoire.';
+
+                $validator->errors()->add('client_id', $message);
+                $validator->errors()->add('group_id', $message);
+            }
+
+            if ($hasClient && $hasGroup) {
+                $message = 'Selectionnez soit un client, soit un groupe de clients.';
+
+                $validator->errors()->add('client_id', $message);
+                $validator->errors()->add('group_id', $message);
+            }
+        });
+    }
+
     public function messages(): array
     {
         return [
-            'client_id.required' => 'Le client est obligatoire.',
             'client_id.exists' => 'Le client sélectionné est invalide.',
             'group_id.exists' => 'Le groupe sélectionné est invalide.',
             'status.required' => 'Le statut est obligatoire.',
diff --git a/thanasoft-back/app/Http/Requests/UpdateInvoiceRequest.php b/thanasoft-back/app/Http/Requests/UpdateInvoiceRequest.php
index 6bba608..a996b5a 100644
--- a/thanasoft-back/app/Http/Requests/UpdateInvoiceRequest.php
+++ b/thanasoft-back/app/Http/Requests/UpdateInvoiceRequest.php
@@ -24,7 +24,7 @@ class UpdateInvoiceRequest extends FormRequest
         $invoiceId = $this->route('invoice');
 
         return [
-            'client_id' => 'sometimes|exists:clients,id',
+            'client_id' => 'nullable|exists:clients,id',
             'group_id' => 'nullable|exists:client_groups,id',
             'source_quote_id' => 'nullable|exists:quotes,id',
             'invoice_number' => 'sometimes|string|max:191|unique:invoices,invoice_number,' . $invoiceId,
@@ -64,4 +64,30 @@ class UpdateInvoiceRequest extends FormRequest
             'e_invoice_status.in' => 'Le statut de facturation électronique est invalide.',
         ];
     }
+
+    public function withValidator($validator): void
+    {
+        $validator->after(function ($validator) {
+            if (! $this->hasAny(['client_id', 'group_id'])) {
+                return;
+            }
+
+            $hasClient = filled($this->input('client_id'));
+            $hasGroup = filled($this->input('group_id'));
+
+            if (! $hasClient && ! $hasGroup) {
+                $message = 'Un client ou un groupe de clients est obligatoire.';
+
+                $validator->errors()->add('client_id', $message);
+                $validator->errors()->add('group_id', $message);
+            }
+
+            if ($hasClient && $hasGroup) {
+                $message = 'Selectionnez soit un client, soit un groupe de clients.';
+
+                $validator->errors()->add('client_id', $message);
+                $validator->errors()->add('group_id', $message);
+            }
+        });
+    }
 }
diff --git a/thanasoft-back/app/Repositories/InvoiceRepository.php b/thanasoft-back/app/Repositories/InvoiceRepository.php
index b6c1539..80ed82e 100644
--- a/thanasoft-back/app/Repositories/InvoiceRepository.php
+++ b/thanasoft-back/app/Repositories/InvoiceRepository.php
@@ -25,12 +25,17 @@ class InvoiceRepository extends BaseRepository implements InvoiceRepositoryInter
     {
         return DB::transaction(function () use ($quoteId) {
             // Resolve Quote directly to avoid circular dependency
-            $quote = Quote::with(['client', 'lines'])->find($quoteId);
+            $quote = Quote::with(['client', 'group', 'lines'])->find($quoteId);
             
             if (!$quote) {
                 throw new \Exception("Quote not found");
             }
 
+            $existingInvoice = Invoice::where('source_quote_id', $quote->id)->first();
+            if ($existingInvoice) {
+                return $existingInvoice;
+            }
+
             // Create Invoice
             $invoiceData = [
                 'client_id' => $quote->client_id,
@@ -68,17 +73,19 @@ class InvoiceRepository extends BaseRepository implements InvoiceRepositoryInter
             $this->recordHistory($invoice->id, null, 'brouillon', 'Created from Quote ' . $quote->reference);
 
             try {
-                $this->timelineRepository->logActivity([
-                    'client_id' => $invoice->client_id,
-                    'actor_type' => 'user',
-                    'actor_user_id' => auth()->id(),
-                    'event_type' => 'invoice_created',
-                    'entity_type' => 'invoice',
-                    'entity_id' => $invoice->id,
-                    'title' => 'Nouvelle facture créée',
-                    'description' => "Une facture a été créée à partir du devis #{$quote->id}.",
-                    'created_at' => now(),
-                ]);
+                if ($invoice->client_id !== null) {
+                    $this->timelineRepository->logActivity([
+                        'client_id' => $invoice->client_id,
+                        'actor_type' => 'user',
+                        'actor_user_id' => auth()->id(),
+                        'event_type' => 'invoice_created',
+                        'entity_type' => 'invoice',
+                        'entity_id' => $invoice->id,
+                        'title' => 'Nouvelle facture créée',
+                        'description' => "Une facture a été créée à partir du devis #{$quote->id}.",
+                        'created_at' => now(),
+                    ]);
+                }
             } catch (\Exception $e) {
                 Log::error("Failed to log invoice creation activity: " . $e->getMessage());
             }
@@ -91,7 +98,7 @@ class InvoiceRepository extends BaseRepository implements InvoiceRepositoryInter
 
     public function all(array $columns = ['*']): \Illuminate\Support\Collection
     {
-        return $this->model->with(['client', 'lines.product'])->get($columns);
+        return $this->model->with(['client', 'group', 'lines.product'])->get($columns);
     }
 
     public function create(array $data): Invoice
@@ -113,17 +120,19 @@ class InvoiceRepository extends BaseRepository implements InvoiceRepositoryInter
                 $this->recordHistory($invoice->id, null, $invoice->status, 'Invoice created');
 
                 try {
-                    $this->timelineRepository->logActivity([
-                        'client_id' => $invoice->client_id,
-                        'actor_type' => 'user',
-                        'actor_user_id' => auth()->id(),
-                        'event_type' => 'invoice_created',
-                        'entity_type' => 'invoice',
-                        'entity_id' => $invoice->id,
-                        'title' => 'Nouvelle facture créée',
-                        'description' => "La facture #{$invoice->id} a été créée.",
-                        'created_at' => now(),
-                    ]);
+                    if ($invoice->client_id !== null) {
+                        $this->timelineRepository->logActivity([
+                            'client_id' => $invoice->client_id,
+                            'actor_type' => 'user',
+                            'actor_user_id' => auth()->id(),
+                            'event_type' => 'invoice_created',
+                            'entity_type' => 'invoice',
+                            'entity_id' => $invoice->id,
+                            'title' => 'Nouvelle facture créée',
+                            'description' => "La facture #{$invoice->id} a été créée.",
+                            'created_at' => now(),
+                        ]);
+                    }
                 } catch (\Exception $e) {
                     Log::error("Failed to log manual invoice creation activity: " . $e->getMessage());
                 }
@@ -176,7 +185,7 @@ class InvoiceRepository extends BaseRepository implements InvoiceRepositoryInter
 
     public function find(int|string $id, array $columns = ['*']): ?Invoice
     {
-        return $this->model->with(['client', 'lines.product', 'history.user'])->find($id, $columns);
+        return $this->model->with(['client', 'group', 'lines.product', 'history.user'])->find($id, $columns);
     }
 
     private function recordHistory(int $invoiceId, ?string $oldStatus, string $newStatus, ?string $comment = null): void
diff --git a/thanasoft-back/app/Repositories/QuoteRepository.php b/thanasoft-back/app/Repositories/QuoteRepository.php
index c1544cc..9fec950 100644
--- a/thanasoft-back/app/Repositories/QuoteRepository.php
+++ b/thanasoft-back/app/Repositories/QuoteRepository.php
@@ -95,18 +95,10 @@ class QuoteRepository extends BaseRepository implements QuoteRepositoryInterface
                          
                          // Auto-create invoice when status changes to 'accepte'
                          if ($newStatus === 'accepte' && $oldStatus !== 'accepte') {
-                             try {
-                                 $this->invoiceRepository->createFromQuote($id);
-                                 Log::info('Invoice auto-created from quote', ['quote_id' => $id]);
-                             } catch (\Exception $e) {
-                                 Log::error('Failed to auto-create invoice from quote: ' . $e->getMessage(), [
-                                     'quote_id' => $id,
-                                     'exception' => $e,
-                                 ]);
-                                 // Don't throw - quote update should still succeed
-                             }
+                             $this->invoiceRepository->createFromQuote($id);
+                             Log::info('Invoice auto-created from quote', ['quote_id' => $id]);
                          }
-                    }
+                     }
                 }
 
                 return $updated;
diff --git a/thanasoft-back/database/migrations/2026_04_02_151000_make_invoice_client_nullable.php b/thanasoft-back/database/migrations/2026_04_02_151000_make_invoice_client_nullable.php
new file mode 100644
index 0000000..8e25eb4
--- /dev/null
+++ b/thanasoft-back/database/migrations/2026_04_02_151000_make_invoice_client_nullable.php
@@ -0,0 +1,28 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    /**
+     * Run the migrations.
+     */
+    public function up(): void
+    {
+        Schema::table('invoices', function (Blueprint $table) {
+            $table->unsignedBigInteger('client_id')->nullable()->change();
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     */
+    public function down(): void
+    {
+        Schema::table('invoices', function (Blueprint $table) {
+            $table->unsignedBigInteger('client_id')->nullable(false)->change();
+        });
+    }
+};
diff --git a/thanasoft-front/src/components/Organism/Invoice/InvoiceDetailPresentation.vue b/thanasoft-front/src/components/Organism/Invoice/InvoiceDetailPresentation.vue
index d692b54..dd269c6 100644
--- a/thanasoft-front/src/components/Organism/Invoice/InvoiceDetailPresentation.vue
+++ b/thanasoft-front/src/components/Organism/Invoice/InvoiceDetailPresentation.vue
@@ -56,7 +56,7 @@
         </div>
         <div>
           <h6 class="text-lg mb-0 mt-1">
-            {{ invoice.client?.name || "Client inconnu" }}
+            {{ recipientName }}
           </h6>
           <p class="text-sm mb-3">
             {{ invoice.lines?.length || 0 }} ligne(s) dans cette facture.
@@ -109,18 +109,18 @@
         >
           <div class="d-flex flex-column">
             <h6 class="mb-3 text-sm">
-              {{ invoice.client?.name || "Client inconnu" }}
+              {{ recipientName }}
             </h6>
             <span class="mb-2 text-xs">
               Adresse email :
               <span class="text-dark ms-2 font-weight-bold">{{
-                invoice.client?.email || "—"
+                invoice.client?.email || groupDetailsFallback
               }}</span>
             </span>
             <span class="mb-2 text-xs">
               Téléphone :
               <span class="text-dark ms-2 font-weight-bold">{{
-                invoice.client?.phone || "—"
+                invoice.client?.phone || groupDetailsFallback
               }}</span>
             </span>
             <span class="text-xs">
@@ -159,7 +159,7 @@
 </template>
 
 <script setup>
-import { ref, onMounted, defineProps } from "vue";
+import { computed, ref, onMounted, defineProps } from "vue";
 import { useInvoiceStore } from "@/stores/invoiceStore";
 import { useNotificationStore } from "@/stores/notification";
 import InvoiceDetailTemplate from "@/components/templates/Invoice/InvoiceDetailTemplate.vue";
@@ -185,6 +185,16 @@ const error = ref(null);
 const selectedStatus = ref("brouillon");
 let invoiceStatusRequestId = 0;
 
+const recipientName = computed(() => {
+  if (invoice.value?.client?.name) return invoice.value.client.name;
+  if (invoice.value?.group?.name) return invoice.value.group.name;
+  return "Client inconnu";
+});
+
+const groupDetailsFallback = computed(() => {
+  return invoice.value?.group?.name ? `Groupe: ${invoice.value.group.name}` : "—";
+});
+
 const load = async () => {
   loading.value = true;
   error.value = null;
diff --git a/thanasoft-front/src/components/Organism/Quote/QuoteDetailPresentation.vue b/thanasoft-front/src/components/Organism/Quote/QuoteDetailPresentation.vue
index b3f35fc..bbe0f19 100644
--- a/thanasoft-front/src/components/Organism/Quote/QuoteDetailPresentation.vue
+++ b/thanasoft-front/src/components/Organism/Quote/QuoteDetailPresentation.vue
@@ -335,9 +335,13 @@ const changeStatus = (id, newStatus) => {
     })
     .catch((e) => {
       console.error(e);
+      const message =
+        e?.response?.data?.message ||
+        e?.response?.data?.error ||
+        "Impossible de mettre à jour le statut";
       notificationStore.error(
         "Erreur",
-        "Impossible de mettre à jour le statut",
+        message,
         3000
       );
     })
diff --git a/thanasoft-front/src/services/invoice.ts b/thanasoft-front/src/services/invoice.ts
index ea857a4..069dda7 100644
--- a/thanasoft-front/src/services/invoice.ts
+++ b/thanasoft-front/src/services/invoice.ts
@@ -1,9 +1,10 @@
 import { request } from "./http";
 import { Client } from "./client";
+import type { ClientGroup } from "./clientGroup";
 
 export interface Invoice {
   id: number;
-  client_id: number;
+  client_id: number | null;
   group_id: number | null;
   source_quote_id: number | null;
   invoice_number: string;
@@ -27,6 +28,7 @@ export interface Invoice {
   created_at: string;
   updated_at: string;
   client?: Client;
+  group?: ClientGroup;
 }
 
 export interface InvoiceListResponse {
@@ -61,7 +63,7 @@ export interface InvoiceLine {
 }
 
 export interface CreateInvoicePayload {
-  client_id: number;
+  client_id: number | null;
   group_id?: number | null;
   source_quote_id?: number | null;
   status:
diff --git a/thanasoft-front/tsconfig.tsbuildinfo b/thanasoft-front/tsconfig.tsbuildinfo
index b0db437..9a0bfde 100644
--- a/thanasoft-front/tsconfig.tsbuildinfo
+++ b/thanasoft-front/tsconfig.tsbuildinfo
@@ -477,8 +477,8 @@
         "affectsGlobalScope": false
       },
       "./src/services/invoice.ts": {
-        "version": "80e3771c11bc5a9285a945e823ae6cf3e91d10d6e84026bcebc4c0461d66a4f1",
-        "signature": "803ff09fa250ab40dd95a25dba1f86f3f09a1f4314e0b0c675bd6c046fa859b7",
+        "version": "d74eaedf75a9bd7919401583b1c257b97aab1cf4aca230dd7cb00331dcaeb499",
+        "signature": "4bca8af28c0a39beeeff6fc014cb983a1904406e1020b3a1839da6210cfac5e7",
         "affectsGlobalScope": false
       },
       "./src/services/priceList.ts": {
@@ -623,7 +623,7 @@
       },
       "./src/stores/invoiceStore.ts": {
         "version": "e96532fbe118d5b784d083890259379da5d2c4e956be7eb1d0fcf450dc4e54bd",
-        "signature": "1f51d66178b55624d5f7e4d27e3f0f64f0a9d7a0c1f2984fc558e0839230bfaf",
+        "signature": "cc7dee187f2712a03719c3d47ab10dd5468f769af851931185f129964e578fbf",
         "affectsGlobalScope": false
       },
       "./src/stores/productCategoryStore.ts": {
@@ -883,6 +883,7 @@
       "./src/services/invoice.ts": [
         "./node_modules/tslib/tslib.d.ts",
         "./src/services/client.ts",
+        "./src/services/clientGroup.ts",
         "./src/services/http.ts"
       ],
       "./src/services/priceList.ts": [
@@ -1195,7 +1196,8 @@
         "./src/services/http.ts"
       ],
       "./src/services/invoice.ts": [
-        "./src/services/client.ts"
+        "./src/services/client.ts",
+        "./src/services/clientGroup.ts"
       ],
       "./src/services/quote.ts": [
         "./src/services/client.ts"