Commerce Discount Coupons incorporates Coupon handling into the Commerce Discount module. It borrows liberally from the Commerce Coupons module and its UI for coupon handling at checkout.
Features
"Product Coupon" discount type lets you create and manage discounts and coupons in one place
Leverages all the smarts available to discounts for your coupons, including %off, fixed amount off coupons, date ranges, usage count, application by products, product categories, and anything else you can do with inline conditions
Product Level Coupons (for a "5% off all red hats" coupon, for example)
How to use it
From Admin menu, go to Store | Discounts | Add Discount
From "Choose Discount Type", select Product Coupon
Build your Coupon the same way you would build a Product Discount, including inline conditions, usage and date parameters (which may require installing additional modules.)
Provide a Coupon Code - This is the code your customer will provide at checkout to redeem the coupon and apply it to an order. Keep it simple.
Positioned the Coupons checkout pane so it appears in your site's checkout process. Go to Store | Configuration | Checkout Settings