Receipts and proof of purchase. A receipt or proof of purchase is a document that you provide to your customers as record of their purchase of your goods or services. A receipt can be in the form of a tax invoice, or a printed cash register or hand written receipt. Yes and no. You usually only need proof of purchase when goods are faulty; so abank statement or other proof can take the place of a receipt. If it’s not faulty, you have no rights, therefore if store policy says a receipt’s needed, it’s needed.