how can i block some users from using coupon codes i gave some codes for cheap membership to someone and seems he passed on to many and now out of control
No, there is not option to disallow particalur user to use all coupons. You can limit number of coupon usage to 1 then it does not make sense to share this coupon, with such configuration coupon can be used only once. Another option you can assign specific user to coupon code and only this user will be able to use it.