Open Stripe and click on Product Catalog, then navigate to the Coupon section. From there, click the + Create Coupon button.

Follow the steps below to create coupon.

Select the duration for the coupon.

Set expiration for the coupon. If there is no expiration, leave the box unchecked. Then click Create Coupon to save.

Go to Command Center and navigate to the Sales Management section, then click to the Stripe Cart tab. From there, paste the coupon code into the Coupon section for each product that is included (typically all but the Monthly Lease options). 

Scroll down and click Save.

Warning: Keep an eye on the top of the page to make sure the coupon has been successfully applied.