What is the difference between a 10 and 12 digit INN?

A 10-digit INN belongs to an organisation (legal entity) and has one check digit. A 12-digit INN belongs to an individual or sole trader and has two check digits.

Does a valid checksum mean the company really exists?

No. The check digit only proves the number is internally consistent. It does not confirm the entity is registered with the FNS.

What does the region code mean?

The first two digits of an INN identify the region (subject of the Russian Federation) of the tax office that issued it — for example 77 for Moscow or 78 for Saint Petersburg. The validator reads and shows this code.

How is the INN check digit calculated?

Each digit is multiplied by a fixed weight, the products are summed, and the result is taken modulo 11 then modulo 10 to get the control digit. A 10-digit INN has one such digit; a 12-digit INN has two, each with its own weight set.

Why would a correctly typed INN fail validation?

Usually a typo: a single wrong or transposed digit changes the weighted sum and breaks the checksum. Re-check the number against the source; the validator flags exactly that kind of error.

Russia INN Validator

Q: Is my INN uploaded anywhere?

No. All validation happens locally in your browser and nothing is sent over the network.

The INN (ИНН — taxpayer identification number) is 10 digits for an organisation and 12 digits for an individual or sole trader. The last digit (or last two) is a control digit computed by the Federal Tax Service weighting formula. This tool detects the type, shows the region, and verifies the checksum.

How it works

Each INN type has fixed digit weights. The control digit is computed as (Σ weightᵢ × digitᵢ) mod 11, then mod 10:

10-digit (organisation): one check digit, weights 2 4 10 3 5 9 4 6 8.
12-digit (individual): two check digits. The 11th digit uses weights 7 2 4 10 3 5 9 4 6 8, and the 12th uses 3 7 2 4 10 3 5 9 4 6 8 over all preceding digits.

The validator computes the expected control digit(s) and compares them with the ones in your number. It also reads the first two digits as the region code. A valid checksum proves internal consistency only — it does not confirm registration with the FNS.

Example

For a 10-digit organisation INN, multiply the first nine digits by 2 4 10 3 5 9 4 6 8, sum the products, take mod 11 then mod 10, and the result must equal the 10th digit. If it matches, the checksum is valid.

INN length	Belongs to	Check digits
10 digits	Organisation (legal entity)	1
12 digits	Individual / sole trader	2

All validation happens locally in your browser and nothing is sent over the network.