expression, godan verb (-ku)
to be able to get a discount; to be eligible for a discount
Used when a discount is applicable or can be obtained, often with conditions like membership or coupons.
この会員証があれば、割引が効きます。
If you have this membership card, you can get a discount.
クーポンを使うと割引が効く。
You can get a discount if you use a coupon.