将优惠券等兑换成现金（或物品）
to exchange a piece of paper representing a particular amount of money for that amount of money or for goods to this value
I've never had any issues redeeming coupons there.
You can save quite a lot of money by redeeming these coupons.
You have six weeks left to redeem this voucher.
This voucher can be redeemed for a free set of mugs.
You can redeem the coupons at any of their stores.
You'd be surprised at the number of people who fail to redeem their vouchers for free meals.
See also: redeem (EXCHANGE)