How is the IPN check digit calculated?

Multiply the first 9 digits by the weights −1, 5, 7, 9, 4, 6, 10, 5, 7 and sum the products. Take the sum modulo 11. The check digit is that remainder, except a remainder of 10 maps to 0. It must equal the 10th digit.

What is the difference between IPN and РНОКПП?

They are the same identifier. ІПН (individual tax number) is the older name; РНОКПП (registration number of the taxpayer card) is the current official term. Both refer to the 10-digit number on a Ukrainian tax registration.

Does the IPN encode anything else?

Yes. The first five digits encode the date of birth as the number of days since 31 December 1899, and the ninth digit's parity indicates sex (odd for male, even for female). This validator focuses on the check digit; it does not decode the birth date.

Why does my IPN fail validation?

A failure almost always means a digit was mistyped or transposed, or the number is not 10 digits long. Re-check each digit against the source tax document or Diia record.

Is my IPN sent anywhere?

No. The entire calculation runs locally in your browser. The number never leaves your device.

Ukraine IPN (РНОКПП) Validator

The IPN (ІПН) / РНОКПП is the 10-digit individual taxpayer number Ukraine assigns to each person on their tax registration card. It is used in HR onboarding and Diia digital-identity workflows, and it carries a modulo-11 check digit so transcription errors can be caught instantly. This validator runs the official algorithm in your browser.

How it works

The 10th digit is a check digit derived from the first 9 digits:

Strip non-digits. The number must be exactly 10 digits.
Multiply the first 9 digits by the weights −1, 5, 7, 9, 4, 6, 10, 5, 7 and add the products. (The first weight is negative.)
Take the weighted sum modulo 11.
The check digit is that remainder, except that a remainder of 10 maps to 0.
The IPN is valid when the computed check digit equals the actual 10th digit.

Example

For body digits 1 2 3 4 5 6 7 8 9 with weights -1 5 7 9 4 6 10 5 7:

(1×-1)+(2×5)+(3×7)+(4×9)+(5×4)+(6×6)+(7×10)+(8×5)+(9×7)
= -1 + 10 + 21 + 36 + 20 + 36 + 70 + 40 + 63 = 295
295 mod 11 = 9  → check digit 9

So an IPN ending in 9 for that body passes the check.

Notes

A valid check digit confirms the IPN is internally consistent, not that the taxpayer is registered or active — use official tax / Diia services for that. The first five digits also encode a birth date, but this tool only verifies the check digit. Everything runs locally, so your IPN never leaves your device.