All PETZ users have a PETZ Wallet.  

This wallet holds all the user's saved coupons.  For any coupon to apply to a sale it must be in the PETZ Wallet. For most coupons the path to the wallet is the user saves the coupon.  If a customer thinks a coupon should have applied, this is the first place to look.  If the coupon is not in the wallet, that is the problem.  If the coupon is in the wallet, the wallet provides the coupon details and the UPCs that the coupon applies to.  Most of the time reading the coupon details is enough to identify the issue (wrong size or flavor is common).

Wallet Access

The POS API has access to the raw wallet data available in the /posface/customer/set/endpoint.  This information is enough to build a page to display all of the wallet details, but you don't have to do all of that.  To make POS integration a bit easier PETZ will provide a web url for your POS to display the PETZ Wallet in a webview or iframe.