Display a Custom Message above or before the Coupon field in Review & Submit of Checkout page

To display the custom message above or before the Coupon field in Review & Submit of Checkout page:
1. Navigate to List > Web Site > Tabs
2. Edit the Checkout Tab
3. In Place Order Page Message field, Switch to HTML Mode
4. Enter the sample code below:

 <script language="javascript">var shipAdd = document.getElementById('additionalfieldstable');shipAdd.rows[0].innerHTML="NOTE: Custom Message";</script>

5. Save