diff --git a/configs/constants/constants.go b/configs/constants/constants.go
index 7bfe6b0..8f052e1 100644
--- a/configs/constants/constants.go
+++ b/configs/constants/constants.go
@@ -33,3 +33,7 @@ const (
 	API_PATH_AUTH_LOGIN    = "/login"
 	API_PATH_PROFILE       = "/profile"
 )
+
+const (
+	USER_ID_MIDDLEWARE = "user_id"
+)
diff --git a/internal/middlewares/auth_middleware.go b/internal/middlewares/auth_middleware.go
index ca8af3c..b0cce2c 100644
--- a/internal/middlewares/auth_middleware.go
+++ b/internal/middlewares/auth_middleware.go
@@ -4,6 +4,7 @@ import (
 	"net/http"
 	"strings"
 
+	"wm-backend/configs/constants"
 	"wm-backend/pkg/helper"
 	"wm-backend/response"
 
@@ -48,7 +49,7 @@ func AuthMiddleware() gin.HandlerFunc {
 		}
 
 		// 5. Set user_id in gin context for downstream handlers
-		c.Set("user_id", userID)
+		c.Set(constants.USER_ID_MIDDLEWARE, userID)
 		c.Next()
 	}
 }
diff --git a/internal/services/invoice_service.go b/internal/services/invoice_service.go
index d03439f..6b7ce8d 100644
--- a/internal/services/invoice_service.go
+++ b/internal/services/invoice_service.go
@@ -4,6 +4,7 @@ import (
 	"net/http"
 	"strconv"
 	"time"
+	"wm-backend/configs/constants"
 	"wm-backend/global"
 	"wm-backend/internal/models"
 	"wm-backend/internal/models/requests"
@@ -29,6 +30,7 @@ import (
 // @Failure      500   {object}  response.ErrorResponse
 // @Router       /v1/invoices [post]
 func InvoiceCreate(c *gin.Context) error {
+	userID, _ := c.Get(constants.USER_ID_MIDDLEWARE)
 	requestBody := requests.CreateInvoiceRequest{}
 	if helper.IsShouldBindJSON(c, &requestBody) {
 		return nil
@@ -39,7 +41,7 @@ func InvoiceCreate(c *gin.Context) error {
 		InvoiceConfigID: requestBody.InvoiceConfigID,
 		TotalItems:      requestBody.TotalItems,
 		Note:            requestBody.Note,
-		CreatedBy:       requestBody.CreatedBy,
+		CreatedBy:       userID.(string),
 		ApprovedBy:      requestBody.ApprovedBy,
 		CreatedAt:       time.Now(),
 	}