Usually, Walmart will take any returns without a receipt, but diapers seem to be the exception. Apparently, each store has a different UPC code for the same product. If you've received the wrong size diapers as a gift it can be confusing where to return them. To find out which store the product comes from try using a search engine and put in the UPC code (12 or 13 digit number) or go to searchupc.com. Make sure you put the two smaller numbers at either end in too.