The RNOKPP (Reiestratsiynyy nomer oblikovoyi kartky platnyka podatkiv) is the 10-digit personal tax-account number issued by Ukraine's State Tax Service (DPS). It is also widely called the IPN (identyfikatsiynyy nomer platnyka podatkiv). The number is required for employment contracts, bank accounts, property transactions and most government services. Unlike a random serial, it encodes the holder's date of birth and gender in its structure.

What information is encoded in an RNOKPP?

Digits one through five encode a day count: the number of days elapsed since 31 December 1899, where day one equals 1 January 1900. Adding those days to the base date recovers the holder's full date of birth. Digits six through eight are a sequential serial number within that calendar day. Digit nine encodes gender: an odd value means male, an even value means female. Digit ten is the control (check) digit produced by the weighted MOD-11 formula.

How is the RNOKPP check digit calculated?

The first nine digits are multiplied by the fixed weight vector [-1, 5, 7, 9, 4, 6, 10, 5, 7] and the products are summed. The control digit is (sum mod 11) mod 10. An intermediate mod-11 is used because a raw mod-10 of the sum would give incorrect results for inputs where the weighted sum mod 11 equals 10; the second mod 10 maps that edge case to zero. The tenth digit of the RNOKPP must equal this computed control for the number to be structurally valid.

Does a valid checksum prove the number belongs to a real person?

No. A passing control digit only confirms the number is internally consistent according to the published formula. It does not mean the number is registered with the DPS, that a person with that number exists, or that the decoded date and gender are accurate. Verifying registration requires a query to the official DPS register, which is an online lookup outside the scope of this tool.

Why does this tool report two separate validity checks?

The validator checks two independent conditions. First, it verifies the checksum: does digit ten match the weighted formula? Second, it checks plausibility of the date: does the five-digit day count map to a real calendar date between 1900 and 2100? A number could pass the checksum but contain an impossible day count, or vice versa. Both checks must pass for the result to be marked fully valid.

Is any data sent to a server?

No. All decoding and validation happen locally in your browser using JavaScript. No number you enter is ever transmitted, logged or stored anywhere. This is intentional: a tax identification number is sensitive personal data and should never be sent to a third-party server for validation.

Ukraine RNOKPP Validator

The RNOKPP (Реєстраційний номер облікової картки платника податків — the registration number of the taxpayer’s account card) is Ukraine’s 10-digit personal tax identification number, issued by the State Tax Service. It is also widely called the IPN (Ідентифікаційний номер платника податків). Every employed, banking or property-owning resident needs one. What makes the RNOKPP especially interesting from a data-science perspective is that it is not a random serial: it encodes the holder’s exact date of birth, a daily sequential serial, and a gender indicator — all verifiable with arithmetic alone, entirely in your browser.

How it works

An RNOKPP is exactly 10 decimal digits with a precise internal layout:

Positions	Field	Meaning
1 – 5	Day count	Days elapsed since 31 December 1899
6 – 8	Daily serial	Sequence number within the birth date
9	Gender digit	Odd = male, even = female
10	Control digit	Weighted MOD-11 check digit

Date of birth is recovered by treating the first five digits as a day count with base date 31 December 1899, so day 00001 is 1 January 1900, day 36524 is 31 December 1999, and so on. The tool converts this count to a full calendar date using standard UTC arithmetic — no lookup tables required.

Gender is a single-bit flag embedded in digit nine: any odd digit (1, 3, 5, 7, 9) means male; any even digit (0, 2, 4, 6, 8) means female.

The checksum formula

The control digit in position ten is produced by a weighted MOD-11 algorithm specified in the official DPS registration documentation:

W = [−1, 5, 7, 9, 4, 6, 10, 5, 7]

sum = d1 × (−1) + d2 × 5 + d3 × 7 + d4 × 9 + d5 × 4

d6 × 6 + d7 × 10 + d8 × 5 + d9 × 7

control = (sum mod 11) mod 10

The intermediate mod 11 prevents an impossible single-digit result (the raw sum can be negative or large). The final mod 10 collapses any value of 10 — which cannot appear as a single decimal digit — to zero.

Worked example

Take the obviously-fake number 3104700111:

Digits 1–5: 31047 → 31,047 days after 31 Dec 1899 = 1 January 1985
Digits 6–8: 001 → serial 001 within that day
Digit 9: 1 (odd) → Male
Checksum:

Pos	Digit	Weight	Product
1	3	−1	−3
2	1	5	5
3	0	7	0
4	4	9	36
5	7	4	28
6	0	6	0
7	0	10	0
8	1	5	5
9	1	7	7
Sum			78

78 mod 11 = 1 → 1 mod 10 = 1 — matches digit ten, so the checksum passes.

This number was constructed specifically for this demonstration and does not correspond to any real person.

Privacy note

Everything in this tool runs locally inside your browser using JavaScript. No number you enter is transmitted, logged or stored anywhere. Tax identification numbers are sensitive personal data — this tool is designed so you never have to share yours with a third party just to check its structure.