A Vietnamese tax code (Mã số thuế, MST) is the identifier the General Department of Taxation issues to every enterprise and individual taxpayer. Enterprises receive a 10-digit code, and each branch or dependent unit receives a 13-digit code built from the parent’s 10 digits plus a 3-digit branch number. Before relying on an MST on a Vietnamese electronic invoice (hóa đơn điện tử) or supplier record, you can confirm it is well-formed with the official check-digit rule. This free validator runs that exact check in your browser.
How it works
The tenth digit of the 10-digit base is a check digit:
- Strip any dashes and spaces.
- Multiply the first nine digits by the weights 31, 29, 23, 19, 17, 13, 7, 5, 3.
- Add the nine products to get the weighted sum.
- Compute
11 - (sum mod 11). If the result is 11 it maps to 0; if the result is 10 the code is invalid because such a check digit is never issued. - The MST is valid when that value equals the tenth digit.
For a 13-digit branch code, the first 10 digits are validated the same way and the final 3 digits are the branch sequence number.
Example
For an enterprise MST, suppose the first nine digits produce a weighted sum of 295. Then 295 mod 11 = 9, so the expected check digit is 11 - 9 = 2. If the tenth digit is 2, the code passes; otherwise it fails.
A valid check digit confirms the MST is well-formed, not that the taxpayer is registered or active. For e-invoice compliance, confirm the status via the official tax portal. Everything here runs locally — your tax code never leaves your device.