Six months. According to the regulations of Shenzhen Taxation Bureau, the invoice of title machine is valid for six months. Units and individuals that issue invoices need to store and keep invoices in accordance with the provisions of the tax authorities, and shall not damage them without authorization. The issued invoice stub and invoice register need to be kept for 5 years. After the expiration of the preservation period, it shall be destroyed after inspection by the tax authorities. Invoices shall be issued in accordance with the prescribed time limit, sequence and columns, all of which shall be issued at one time and stamped with special invoices.