diff --git a/repositories/invoice/InvoiceRepository.js b/repositories/invoice/InvoiceRepository.js
index 580814b..0d30f30 100644
--- a/repositories/invoice/InvoiceRepository.js
+++ b/repositories/invoice/InvoiceRepository.js
@@ -1,13 +1,23 @@
 const pool = require('../../database/database');
 const Invoice = require('../../models/Invoice');
 
-function genInvoiceNumber() {
-  const now = new Date();
-  const y = now.getFullYear();
-  const m = String(now.getMonth() + 1).padStart(2, '0');
-  const d = String(now.getDate()).padStart(2, '0');
-  const rand = Math.floor(Math.random() * 1e6).toString().padStart(6, '0');
-  return `INV-${y}${m}${d}-${rand}`;
+async function genInvoiceNumber() {
+  const year = new Date().getFullYear();
+  const prefix = `RE-${year}-`;
+  const [rows] = await pool.query(
+    `SELECT invoice_number FROM invoices
+     WHERE invoice_number LIKE ?
+     ORDER BY CAST(SUBSTRING_INDEX(invoice_number, '-', -1) AS UNSIGNED) DESC
+     LIMIT 1`,
+    [`${prefix}%`],
+  );
+  let next = 1;
+  if (rows.length) {
+    const last = rows[0].invoice_number; // e.g. RE-2026-01032026
+    const num = parseInt(last.split('-').pop(), 10);
+    if (!isNaN(num)) next = num + 1;
+  }
+  return `${prefix}${String(next).padStart(8, '0')}`;
 }
 
 class InvoiceRepository {
@@ -32,7 +42,7 @@ class InvoiceRepository {
     const conn = await pool.getConnection();
     try {
       await conn.beginTransaction();
-      const invoice_number = genInvoiceNumber();
+      const invoice_number = await genInvoiceNumber();
 
       // compute totals
       let total_net = 0;