The OIB (Osobni identifikacijski broj) is Croatia’s 11-digit personal and business identification number, used for tax and government records. It is randomly assigned and carries no date of birth or gender, so the only thing verifiable offline is its check digit. This validator recomputes that digit and confirms whether it matches — useful for catching typos in forms and data, without contacting any registry.
How it works
An OIB is 11 digits: the first ten form the base number and the eleventh is a check digit computed with the ISO 7064 MOD 11,10 algorithm. Starting with a remainder of 10, for each of the first ten digits the tool computes t = (remainder + digit) mod 10 (treating 0 as 10), then remainder = (t × 2) mod 11. The check digit is (11 − remainder) mod 10. The validator compares this expected digit against the eleventh digit you entered.
Example
For the base number 1234567890, the algorithm yields a check digit of 3, so 12345678903 is a well-formed OIB. If you entered 12345678904, the validator would flag it invalid and report 3 as the correct check digit.
Paste a number and this tool computes the expected check digit and confirms whether it matches — all in your browser, with nothing uploaded.