Stacking coupons refers to using both a store coupon and a manufacturer coupon on one product, which nearly all stores allow. Only one manufacturer coupon may be used per item. Here is an example of coupon stacking:
Buy 1 Arm & Hammer Laundry Detergent $3.50, sale price
Use $0.75/1 Arm & Hammer Laundry Detergent from SmartSource insert 7/15
And $1.00/1 Arm & Hammer Laundry Item store coupon
Final Price: $1.75
Keep any eye out for store coupons. These can be found in many locations, including ad circulars, website printables (such as BJ's Wholesale Club, Meijer Mealbox, Rite Aid, Target, and Whole Foods), in-store booklets, Sunday newspaper inserts, or via a mobile device. Then match these up with manufacturer coupons found in magazines, newspaper inserts, mailers, tearpads, peelies, blinkies, and printables from sites like Coupons.com, CouponNetwork.com, RedPlum.com, and SmartSource.com. When you combine store and manufacturer coupons, the savings really add up!
As per their coupon policy, Rite Aid will allow you to stack 3 coupons: one "RC48″ coupon, one "RC49″ coupon, and one manufacturer coupon on a single item.
Some Food Lion, Giant Eagle, Whole Foods, and Kmart locations do not allow stacking a clipped store coupon with a manufacturer coupon, so see your store for details.
When price matching at Walmart, stacking is not allowed because you may only use one coupon per item.