The tax number refers to the tax registration number of the enterprise in China. It can be understood as the company's identity card. The tax registration certificate number consists of six administrative division codes plus nine organization codes, which is generally a number of 15. The number code of the tax registration certificate has now risen to 18, that is, all kinds of enterprises and organizations, taxpayers and withholding agents apply the 9-digit organization code compiled by the State Bureau of Technical Supervision, with the 6-digit administrative region code of the national standard in front and the 3-digit special code of the tax authorities behind as the number code of the tax registration certificate. After the original tax registration number 15 digits, three sequential codes are added, which are mainly used for tax registration with 15 personal ID card for branches without code certificate of technical supervision bureau (such as community branches) and individual industrial and commercial households with multiple business premises (with independent business licenses); For individual industrial and commercial households that use 18 employees to operate multiple business premises (with independent business licenses) and have fixed business premises, after consultation with the municipal technical supervision department, the tax authorities may issue a "co-organizer" for taxpayers and may apply for an organization code certificate. The last three digits of the tax registration number of other units are still three zeros.

This tax number is currently mainly used in Latin American countries, especially Mexico. At present, Mexican customs clearance needs this domestic number, and Brazil and other countries also need it, but the name may be different and needs specific confirmation.