Four years. Invoice refers to the 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, which is the original basis of accounting. Jinsui invoicing software can find invoices four years ago. Invoicing is a tax payment voucher, a special voucher used by tax authorities to collect taxes from taxpayers according to the tax law, and a legal proof that taxpayers fulfill their tax obligations according to law.