DigiKitTurkish Tax ID (VKN) Validator
Enter the 10-digit tax ID to see whether its last digit satisfies the check rule.
How is a Turkish tax ID validated?
The last digit of a 10-digit tax ID is a check digit calculated from the first nine. The tool performs this calculation and compares it with the last digit you entered. The calculation is:
- For each digit (from the left, i = 0 ... 8) compute t = (digit + (9 − i)) mod 10.
- If t is zero the contribution is 0. Otherwise take the remainder of t × 2(9 − i) divided by 9; if the remainder is 0 the contribution is 9.
- Add the nine contributions.
- The check digit is (10 − sum mod 10) mod 10 and is compared with the number's last digit.
Worked example
A number known to satisfy the rule is 4540536920:
| i | Digit | t | Contribution |
|---|---|---|---|
| 0 | 4 | 3 | 6 |
| 1 | 5 | 3 | 3 |
| 2 | 4 | 1 | 2 |
| 3 | 0 | 6 | 6 |
| 4 | 5 | 0 | 0 |
| 5 | 3 | 7 | 4 |
| 6 | 6 | 9 | 9 |
| 7 | 9 | 1 | 4 |
| 8 | 2 | 3 | 6 |
The contributions add up to 40. The check digit is (10 − 40 mod 10) mod 10 = 0, which equals the number's last digit. If the last digit were 1 (4540536921) the number would be invalid.
Things to keep in mind
- The tool only checks the check digit; it does not show whether the number belongs to a taxpayer.
- Individuals usually transact with their national ID number; for 11-digit numbers use the Turkish ID Number Validator.
- When writing the number on invoices and documents, compare it with the official record.
Tax ID number versus national ID number
A Turkish tax identification number (VKN) has 10 digits and is issued to legal entities such as companies and to people with a tax registration. For individuals in Turkey, the 11-digit national ID number (TC kimlik no) also serves as the tax number.
This tool checks whether a number is structurally valid, meaning the digits follow the rule. To find out whether it actually belongs to a registered, active taxpayer, use the tax ID lookup on the Turkish Revenue Administration's online tax office.
Frequently asked questions
How many digits is a tax ID?
10 digits: the first nine and the last digit, which is the check digit. Individuals mostly use their national ID number, while companies use a 10-digit tax identification number.
Does the tool look up the taxpayer?
No. It only computes whether the last digit satisfies the check rule. To learn whether a number belongs to a taxpayer, use the Revenue Administration's lookup services.
Must a valid number be registered?
No. A number that satisfies the rule may not be registered. The result only helps catch typing mistakes.
Why is the last digit important?
It is calculated from the first nine digits. If one digit is mistyped, the calculated check digit no longer matches and the number looks invalid.