Stacking coupons means you are using more than one coupon per purchase. Stacking of coupons can be done at certain stores, while other stores do NOT allow it! This process varies by store, so make sure to check out the Coupon Policies to make sure you are doing it the right way!
Since most BOGO (or similar) manufacturer coupons include the phrase “Limit 1 coupon per purchase”, you CANNOT use a 2nd manufacturer coupon to stack. Most stacked coupons will be a store coupon with a manufacturer coupon.