We need a proper paper trail for our purchases but are only offered receipts

As foster parents we have to have proof of what we buy but were only offered an e-receiptMy wife and I are foster carers and need to provide receipts for any clothes we purchase. We went into River Island in Peterborough but the sales assistant refused to give us a paper receipt. My wife did give her email, but nothing has been received, so if there is a problem we have no proof of purchase. Can I insist on a paper receipt? MD, Spalding, LincsRetailers have gradually been cutting back on the bil