Invoice refers to the text issued by the seller to the buyer in economic activities, including the name, quality and agreed price of the products or services provided to the buyer. In addition to the advance payment, the invoice must also include the money paid by the buyer to the seller according to the agreed conditions, and must include the date and quantity, which is an important proof of accounting. According to China's accounting system, valid invoices for purchasing products or services are called tax invoices. The charging vouchers of government departments have different names in different periods and different charging items, but most of them are collectively referred to as administrative fee receipts. For internal audit and verification, each invoice must have a unique journal number to prevent duplicate or skip invoices. Simply put, an invoice is the original proof of the cost, expense or income incurred. For the company, the invoice is mainly the basis for the company to make accounts, and it is also the proof of tax payment, while for employees, the invoice is mainly used for reimbursement. Simply put, an invoice is the original proof of the cost, expense or income incurred. For the company, the invoice is mainly the basis for the company to make accounts, and it is also the expense certificate for paying taxes; For employees, invoices are mainly used for reimbursement. How to invoice from the invoice qualification, mainly divided into tax agents and self-invoicing.