How many digits is a Greek AFM?

A Greek AFM (Arithmos Forologikou Mitroou) is exactly nine digits. Leading zeros count, so 090000045 is a valid length even though it looks like eight significant digits.

How is the AFM check digit calculated?

Take the first eight digits. Multiply the leftmost by 256, the next by 128, then 64, 32, 16, 8, 4, and 2 — descending powers of two from 2^8 down to 2^1. Sum the products, take that sum modulo 11, then take the result modulo 10. That final value must equal the ninth digit.

Why modulo 11 then modulo 10?

Modulo 11 can produce a remainder of 10, which is not a single digit. Taking modulo 10 afterwards maps the rare value 10 back to 0, ensuring the check digit is always a single digit from 0 to 9.

Does a valid AFM mean the person is registered?

No. The check digit only confirms the number is internally consistent. It does not confirm the AFM is issued to an active taxpayer. Greek authorities confirm registration through their own systems.

Is the AFM the same as the VAT number?

For Greek VAT purposes the AFM is prefixed with the country code EL to form the VAT number. The nine digits and their check digit are identical — only the EL prefix is added.

Greece AFM Tax Number Validator

The Greek AFM (Arithmos Forologikou Mitroou) is the nine-digit tax registration number every individual and business in Greece holds. It appears on invoices, employment contracts, and public-service forms, and the same digits form the EL VAT number. Before trusting an AFM, you can confirm it is internally well-formed using the official modulus-11 check, run here entirely in your browser.

How it works

The ninth digit of an AFM is a check digit derived from the first eight:

Take the first eight digits d1 ... d8.
Weight them by descending powers of two: d1 x 256, d2 x 128, d3 x 64, d4 x 32, d5 x 16, d6 x 8, d7 x 4, d8 x 2.
Sum the eight products.
Compute (sum mod 11) mod 10.
That value must equal the ninth digit.

The double reduction handles the case where sum mod 11 equals 10: the extra mod 10 maps it back to 0.

Example

Validate 090000045 with first eight digits 0 9 0 0 0 0 0 4.

Weighted sum: (0x256)+(9x128)+(0x64)+(0x32)+(0x16)+(0x8)+(0x4)+(4x2) = 1152 + 8 = 1160. 1160 mod 11 = 5, and 5 mod 10 = 5. The ninth digit is 5, so the AFM is valid.

Notes

A valid check digit confirms structure, not active registration. Everything runs locally, so the AFM never leaves your device.