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P&T Europe Services

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Czech birth number validator

Check whether a Czech birth number (rodné číslo) is formally valid. The tool verifies divisibility by eleven and the date of birth, and derives the date of birth, sex and age.

Input

The slash is optional. Birth numbers assigned before 1954 have 9 digits.

A birth number is personal data. The check runs entirely in your browser — nothing is sent to a server or stored.

Validation result

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How a birth number is structured

The rules are set by Section 13 of Act No. 133/2000 Coll. on population registration and birth numbers. A birth number has ten digits written as YYMMDD/XXXX:

  • • YY — the last two digits of the year of birth
  • • MM — the month of birth, increased by 50 for women
  • • DD — the day of birth
  • • XXXX — a four-digit suffix distinguishing people born on the same day; the last digit is the check digit

Numbers assigned before 1 January 1954 have nine digits with a three-digit suffix and contain no check digit — only the date of birth can be verified.

The divisibility check

A ten-digit birth number must be divisible by eleven without a remainder. The check (last) digit equals the remainder of the first nine digits divided by eleven. For example 850314/1240 is divisible by eleven and passes — whereas 850314/1241 does not, and the tool reports a likely typo.

Two exceptions worth knowing

  • • Historical exception (until 1985) — if the remainder of the first nine digits divided by eleven was 10, the check digit 0 was used. Such a number is not divisible by eleven yet is valid. The practice stopped in 1985 and concerns roughly a thousand numbers.
  • • Alternative month (since 2004) — when the range for a given day runs out, 20 is added for men and 70 for women. A man born in March may therefore have month 23, a woman 73.

Why it matters in payroll

In payroll and HR the birth number is used when registering an employee for insurance, on payroll records and in filings. A mistyped birth number is one of the most common reasons filings get rejected — a quick check catches it before the submission goes out.

Personal data

A birth number is personal data governed by Act No. 133/2000 Coll. and the GDPR. This tool therefore works entirely in your browser — the number entered is never sent to a server, stored or processed further.

Official sources

The tool verifies formal correctness only. A valid format does not mean the number was actually assigned to a particular person — only the population register administrator can confirm that.

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Frequently asked questions

How is a Czech birth number validated? +

Under Section 13 of Act No. 133/2000 Coll., a birth number has ten digits and must be divisible by eleven without a remainder. The date of birth must also make sense: the first pair is the year, the second the month (increased by 50 for women) and the third the day. Birth numbers assigned before 1 January 1954 have nine digits and no check digit — only the date can be verified for those.

Why is the month 50 higher for women? +

Adding 50 to the month is how the birth number encodes sex. A woman born in March has month 53 in her birth number. Since 2004, when the range of numbers for a given day runs out, an alternative form is used — the month is increased by 20 for men and by 70 for women.

What if the number is not divisible by eleven? +

Most often it is a typo. There is, however, a historical exception: if the remainder of the first nine digits divided by eleven was 10, the check digit 0 was used, and the whole number is then not divisible by eleven. This was only done until 1985 and concerns roughly a thousand numbers — the tool flags it separately.

Does a valid format mean the number belongs to someone? +

No. The check only verifies the structure, the date of birth and the check digit. It says nothing about whether the number was actually assigned to a particular person — only the population register administrator can confirm that.

Is the birth number sent anywhere? +

No. A birth number is personal data and the entire check runs in your browser. Nothing is sent to a server, stored or processed further.

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