On the ‘SECURE BOOKING’ page you can click “Enter a coupon or promotional code” as shown below.
On the main page, click Car Only, then click SHOW OPTIONS. A drop-down menu will appear from which you can choose the rental company and then enter the coupon.
On the payment page, immediately after the heading HOW WOULD YOU LIKE TO PAY, you will find a link.
You cannot use discount coupons when booking flights or cruises on Orbitz.com. If you are in possession of a discount coupon that claims it’s valid for flights or cruises on Orbitz, follow the instructions laid out by the organization that issued the coupon. Those instructions may include phoning a certain number or accessing a specific website other than the Orbitz main site.