The purpose of entering mobile phone number in electronic catering invoice is to provide the information of the other party when invoicing. Ordinary invoice, just ask the other party's name. For VAT invoices, you need to ask for the full name, address, telephone number, basic bank account number, bank, tax registration number, etc. Invoices usually refer to invoices, which refer to business vouchers issued and collected by all units and individuals in buying and selling goods, providing or receiving services and engaging in other business activities. It is the original basis of accounting, and it is also an important basis for law enforcement inspection by audit institutions and tax authorities.