diff --git a/prisma/schema.prisma b/prisma/schema.prisma
index 1f269d9..fa36549 100644
--- a/prisma/schema.prisma
+++ b/prisma/schema.prisma
@@ -1582,6 +1582,8 @@ enum CreditNoteStatus {
 model CreditNote {
   id String @id @default(cuid())
 
+  code String
+
   creditNoteStatus CreditNoteStatus @default(Pending)
 
   value Float @default(0)
diff --git a/src/controllers/08-credit-note-controller.ts b/src/controllers/08-credit-note-controller.ts
index 38a6eef..5e2b5f7 100644
--- a/src/controllers/08-credit-note-controller.ts
+++ b/src/controllers/08-credit-note-controller.ts
@@ -261,29 +261,47 @@ export class CreditNoteController extends Controller {
       return a + c.productService.product.price;
     }, 0);
 
-    const record = await prisma.creditNote.create({
-      include: {
-        requestWork: {
-          include: {
-            request: true,
-          },
-        },
-        quotation: true,
-      },
-      data: {
-        value,
-        requestWork: {
-          connect: body.requestWorkId.map((v) => ({
-            id: v,
-          })),
-        },
-        quotationId: body.quotationId,
-      },
-    });
-
     this.setStatus(HttpStatus.CREATED);
 
-    return record;
+    return await prisma.$transaction(
+      async (tx) => {
+        const currentYear = new Date().getFullYear();
+        const currentMonth = new Date().getMonth() + 1;
+
+        const last = await tx.runningNo.upsert({
+          where: {
+            key: `CREDIT_NOTE_${currentYear.toString().padStart(2, "0")}${currentMonth.toString().padStart(2, "0")}`,
+          },
+          create: {
+            key: `CREDIT_NOTE_${currentYear.toString().padStart(2, "0")}${currentMonth.toString().padStart(2, "0")}`,
+            value: 1,
+          },
+          update: { value: { increment: 1 } },
+        });
+
+        return await prisma.creditNote.create({
+          include: {
+            requestWork: {
+              include: {
+                request: true,
+              },
+            },
+            quotation: true,
+          },
+          data: {
+            code: `CN${currentYear.toString().padStart(2, "0")}${currentMonth.toString().padStart(2, "0")}${last.value.toString().padStart(6, "0")}`,
+            value,
+            requestWork: {
+              connect: body.requestWorkId.map((v) => ({
+                id: v,
+              })),
+            },
+            quotationId: body.quotationId,
+          },
+        });
+      },
+      { isolationLevel: Prisma.TransactionIsolationLevel.Serializable },
+    );
   }
 
   @Put("{creditNoteId}")