diff --git a/src/Service/AdvertService.php b/src/Service/AdvertService.php
new file mode 100644
index 0000000..f3224c2
--- /dev/null
+++ b/src/Service/AdvertService.php
@@ -0,0 +1,45 @@
+<?php
+
+namespace App\Service;
+
+use App\Entity\Advert;
+use App\Entity\Devis;
+use Doctrine\ORM\EntityManagerInterface;
+
+class AdvertService
+{
+    public function __construct(
+        private OrderNumberService $orderNumberService,
+        private EntityManagerInterface $em,
+    ) {
+    }
+
+    /**
+     * Cree un advert avec un nouveau numero de commande.
+     */
+    public function create(?Devis $devis = null): Advert
+    {
+        $orderNumber = null !== $devis
+            ? $devis->getOrderNumber()
+            : $this->orderNumberService->generateAndUse();
+
+        $advert = new Advert($orderNumber);
+
+        if (null !== $devis) {
+            $advert->setDevis($devis);
+        }
+
+        $this->em->persist($advert);
+        $this->em->flush();
+
+        return $advert;
+    }
+
+    /**
+     * Cree un advert a partir d'un devis existant (meme numero).
+     */
+    public function createFromDevis(Devis $devis): Advert
+    {
+        return $this->create($devis);
+    }
+}
diff --git a/src/Service/DevisService.php b/src/Service/DevisService.php
new file mode 100644
index 0000000..820ecf4
--- /dev/null
+++ b/src/Service/DevisService.php
@@ -0,0 +1,29 @@
+<?php
+
+namespace App\Service;
+
+use App\Entity\Devis;
+use Doctrine\ORM\EntityManagerInterface;
+
+class DevisService
+{
+    public function __construct(
+        private OrderNumberService $orderNumberService,
+        private EntityManagerInterface $em,
+    ) {
+    }
+
+    /**
+     * Cree un devis avec un nouveau numero de commande.
+     */
+    public function create(): Devis
+    {
+        $orderNumber = $this->orderNumberService->generateAndUse();
+        $devis = new Devis($orderNumber);
+
+        $this->em->persist($devis);
+        $this->em->flush();
+
+        return $devis;
+    }
+}
diff --git a/src/Service/FactureService.php b/src/Service/FactureService.php
new file mode 100644
index 0000000..6dba0b9
--- /dev/null
+++ b/src/Service/FactureService.php
@@ -0,0 +1,60 @@
+<?php
+
+namespace App\Service;
+
+use App\Entity\Advert;
+use App\Entity\Facture;
+use Doctrine\ORM\EntityManagerInterface;
+
+class FactureService
+{
+    public function __construct(
+        private OrderNumberService $orderNumberService,
+        private EntityManagerInterface $em,
+    ) {
+    }
+
+    /**
+     * Cree une facture avec un nouveau numero de commande (facture seule).
+     */
+    public function create(?Advert $advert = null): Facture
+    {
+        if (null !== $advert) {
+            return $this->createFromAdvert($advert);
+        }
+
+        $orderNumber = $this->orderNumberService->generateAndUse();
+        $facture = new Facture($orderNumber);
+
+        $this->em->persist($facture);
+        $this->em->flush();
+
+        return $facture;
+    }
+
+    /**
+     * Cree une facture a partir d'un advert (meme numero + splitIndex si plusieurs).
+     */
+    public function createFromAdvert(Advert $advert): Facture
+    {
+        $existingCount = $advert->getFactures()->count();
+
+        $facture = new Facture($advert->getOrderNumber());
+        $facture->setAdvert($advert);
+
+        if ($existingCount > 0) {
+            $facture->setSplitIndex($existingCount + 1);
+
+            // La premiere facture existante doit aussi avoir un splitIndex si elle n'en a pas
+            $firstFacture = $advert->getFactures()->first();
+            if (false !== $firstFacture && 0 === $firstFacture->getSplitIndex()) {
+                $firstFacture->setSplitIndex(1);
+            }
+        }
+
+        $this->em->persist($facture);
+        $this->em->flush();
+
+        return $facture;
+    }
+}