Receipts or invoices after consumption can also be used as vouchers, such as invoices from shopping malls, receipts from POS machines, and consumption vouchers can prove that users use credit cards or loans. Sometimes banks will ask users to provide corresponding consumption vouchers to verify whether users have violated the rules and cashed out. Therefore, users can keep these credentials. It should be noted that no matter what kind of consumption voucher, it must be consistent with the date of consumption, otherwise the bank will regard it as an invalid consumption voucher and need to provide new proof.