Not sure if this is widely known but just found this out. instore & online
How do I use Sainsbury / Safeway vouchers?
We are currently accepting coupons for Sainsbury's and Safeway both in our stores and for on-line Grocery transactions. Just hand your coupons to your driver when your groceries are delivered. We'll credit your payment card back at the store and send you a receipt in the post. If you are in-store, just hand these to the cashier.
We can only accept Sainsbury's or Safeway branded coupons for money off your total transaction.
We cannot accept coupons valid only for specific products or departments.
We can only accept up to £15 worth of coupons for one delivery.
You must have met any requirements on the coupon, such as a minimum spend.
We can only accept them against grocery deliveries. We cannot accept them for deliveries from our warehouses.
We may refuse to accept coupons if they appear to be damaged, defaced, altered or copied.
We cannot accept coupons for purchases of tobacco or infant milk formulae.