How is the Belarusian UNP check digit calculated?

Each of the first eight characters is mapped to a numeric value, multiplied by the weights 29,23,19,17,13,7,5,3, and summed. The remainder modulo 11 is the expected check digit, which must equal the ninth character.

How many characters is a UNP?

Nine characters. Newer UNPs are all digits, while some older codes contain a Latin letter in an early position, which this tool maps to its numeric value before checking.

What if the checksum equals 10?

A control digit of 10 cannot be represented in a single position, so a UNP whose checksum resolves to 10 is treated as invalid by the official rule and rejected here.

Does a valid UNP mean the taxpayer is registered?

No. A valid check digit only confirms the UNP is internally consistent. To confirm the taxpayer is currently registered, check with the MNS of Belarus.

Is my UNP sent anywhere?

No. The check runs entirely in your browser, so the code never leaves your device and nothing is logged or transmitted.

Why does my UNP from a spreadsheet fail validation?

Most often because a leading zero was dropped: spreadsheet number cells strip leading zeros, turning a 9-character UNP into 8 characters. Format the column as text. Cyrillic letters that look like Latin ones (С, О) pasted from Belarusian documents cause the same problem.

What does a failed check digit actually tell me?

That at least one character is wrong — a mistype, a dropped digit, or the wrong identifier entirely (for example an OKPO code instead of a UNP). It cannot tell you which character is wrong; re-check the source document rather than guessing.

What is the Belarus UNP Validator?

Free Belarusian UNP validator. Applies the official 29,23,19,17,13,7,5,3 weighted modulo-11 check-digit algorithm to the 9-character payer's account number used by the MNS for e-invoicing and customs. Runs entirely in your browser. It runs free in your browser on Gera Tools, with nothing uploaded.

Belarus UNP Validator

Name: Belarus UNP Validator
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

The UNP (payer’s account number) is the 9-character taxpayer identifier issued by the Ministry of Taxes and Duties (MNS) of Belarus. It is required on invoices, e-invoicing submissions and customs declarations. The final character is a modulo-11 check digit, so a single mistyped character is detectable. This free validator runs the exact algorithm in your browser.

How the UNP check digit works

The official check-digit algorithm operates on the first eight characters:

Map each character to a numeric value: digits map to themselves, and the Latin letters used in older codes map via a fixed table (A=10, B=11, C=12, E=13, H=14, K=15, M=16, O=17, P=18, T=19).
Multiply each value by its weight: 29, 23, 19, 17, 13, 7, 5, 3.
Sum the products and take the remainder control = sum mod 11.
If control equals 10 the UNP is invalid. Otherwise the ninth character must equal control.

Worked example

Take the candidate UNP 190345677 — first eight characters 19034567, stated check digit 7:

Position	Character	Value	Weight	Product
1	1	1	29	29
2	9	9	23	207
3	0	0	19	0
4	3	3	17	51
5	4	4	13	52
6	5	5	7	35
7	6	6	5	30
8	7	7	3	21
Sum				425

425 mod 11 = 7, which matches the ninth character, so the structure is valid. Change any single character — say the 4 to a 1 — and the sum drops to 386, whose remainder (1) no longer matches, so the tool flags it.

A valid check digit confirms the UNP is well-formed, not that the taxpayer is registered. All processing stays on your device.

Inputs that fail for reasons other than typos

Check digit resolving to 10. The official rule declares such combinations invalid rather than using a two-character check, so some 8-character prefixes simply cannot exist as UNPs. If a supplier’s number consistently fails with an expected check of 10, the whole number is wrong, not just one digit.
Lost leading zeros. A UNP stored in a spreadsheet number cell silently drops a leading zero and arrives as 8 characters. Format UNP columns as text.
Letter lookalikes. Older letter-bearing codes use a restricted alphabet (A, B, C, E, H, K, M, O, P, T). A Cyrillic С or О pasted from a Belarusian document looks identical to the Latin letter but is a different Unicode character — retype the letter if a visually correct code fails.
Confusing UNP with other identifiers. Belarusian documents also carry OKPO codes and bank account numbers; a 9-character string near the company name is not automatically the UNP. The check digit is a good discriminator: genuine UNPs pass, other identifiers usually don’t.

When you need to validate a UNP

E-invoicing and accounting systems. Belarus requires UNP numbers on invoices and reporting documents submitted to the MNS. An accounting system that accepts a malformed UNP will pass the data through to a filing that the tax authority will reject. Catching malformed UNPs at data-entry time avoids downstream filing rejections.

Customs declarations and trade documents. Cross-border trade into and out of Belarus requires counterparty UNP numbers on customs documentation. Importers and freight forwarders who collect supplier UNPs before preparing declarations can use this validator to catch typos before submitting.

B2B data quality. Companies maintaining supplier or customer master records with Belarusian entities should run UNPs through a check-digit validator as part of their data-quality pipeline. A failed check digit is a reliable signal that the number was mistyped during data entry, eliminating a class of errors before they propagate.

The weight sequence and why modulo-11 is used

The weights 29, 23, 19, 17, 13, 7, 5, 3 are all prime numbers, which is intentional. Weighting by primes maximises the detectability of single-character transpositions and substitutions. Modulo-11 was chosen because 11 is prime and produces a check digit ranging from 0 to 10 — with the rule that a result of 10 is declared invalid, rather than requiring two-digit check characters. This makes the algorithm simple to implement and fast to verify manually with a calculator, which was important when the system was designed for manual administrative use.

Sources and references

Ministry of Taxes and Duties of the Republic of Belarus (MNS) — the authority that assigns and maintains UNP numbers
Belarus Business Register (portal.gov.by) — the Unified State Register where a UNP’s registration status can be confirmed

Maintained by the Gera Tools editorial team. The weight sequence and modulo-11 rule are the official UNP check; this tool validates the check digit only and never contacts a register — confirm active registration with the MNS. Last reviewed 2026-07-02.