What does a South African VAT number look like?

A SARS VAT vendor registration number is exactly 10 digits and always starts with the digit 4. The final digit is a Luhn check digit computed over the preceding nine digits.

How is the check digit calculated?

The last digit is a standard Luhn (mod-10) check. Doubling every second digit from the right, subtracting 9 from any result over 9, and summing all digits must produce a total whose units digit is zero.

Why must it start with 4?

SARS allocates VAT vendor numbers in the 4-billion range, so every valid VAT number begins with 4. A number that starts with any other digit is not a VAT vendor number, even if it would otherwise pass Luhn.

Does a valid number mean the vendor is registered?

No. A valid result only confirms the number is structurally correct and passes Luhn. To confirm a vendor is currently VAT-registered, use the SARS VAT vendor search. This tool performs no online lookup.

Is my VAT number sent anywhere?

No. The whole validation runs in your browser using JavaScript. The VAT number never leaves your device, so it is safe for confidential supplier records.

South Africa VAT Number Validator

A South African VAT number is the 10-digit vendor registration number issued by the South African Revenue Service (SARS) to businesses registered for Value-Added Tax. Before you trust one on a tax invoice or supplier record, you can confirm it is well-formed with this free validator, which runs entirely in your browser.

How it works

The validator applies two structural rules plus the Luhn check:

Length. The number must be exactly 10 digits (spaces are ignored).
Leading digit. It must start with 4, the range SARS allocates to VAT vendors.
Luhn check. The final digit is a mod-10 check digit. Working from the right, double every second digit, subtract 9 from any doubled value above 9, sum all the digits, and the total must be a multiple of 10.

Example

Take 4220119988. It is 10 digits and starts with 4, so it passes the structural rules. Running Luhn across all ten digits gives a sum that is a multiple of 10, so the check digit passes and the number is valid.

Notes

A valid result confirms the number is internally consistent — it does not prove the vendor is currently VAT-registered. To confirm registration, use the SARS VAT vendor search. Everything here runs locally, so your VAT number never leaves your device.