It is best for catering enterprises to buy food in supermarkets and issue invoices. If farmers don't have invoices to buy food, they can find ways to issue invoices on behalf of the national tax, so the expenses will be more formal. However, if the amount is not large after one year, it can also be listed in the form of a list, indicating the date, variety, quantity, unit price, amount and other items, and attaching the signature of the seller. Generally, there is no tax recovery in this case. After all, invoicing is not realistic.