What forms can a Czech DIČ take?

A Czech DIČ is CZ followed by the tax identifier. For a legal entity it is an 8-digit IČO with a check digit. For a natural person it is the 9 or 10 digit rodné číslo (national birth number).

How is the IČO check digit calculated?

Multiply the first seven digits by weights 8, 7, 6, 5, 4, 3, 2, sum them, and take modulo 11. The check digit is 1 if the remainder is 0, 0 if the remainder is 1, and otherwise 11 minus the remainder. It must equal the eighth digit.

How is the natural-person form validated?

A natural-person DIČ embeds a rodné číslo. Ten-digit numbers must be divisible by 11 (with the pre-1985 final-zero exception), and nine-digit numbers are checked for a plausible encoded birth date.

Does a valid DIČ mean the entity is VAT-registered?

No. A valid check confirms the number is structurally correct, not that the entity is currently registered for VAT. Use the EU VIES service to confirm active registration.

Is my DIČ sent anywhere?

No. All validation runs in your browser, so the number never leaves your device.

Czech DIČ (VAT) Validator

A Czech DIČ (Daňové identifikační číslo) is the VAT identification number used on invoices and in the EU VIES system. It is the country prefix CZ followed by either a company’s IČO or a person’s rodné číslo. This free validator detects which form you have entered and runs the matching check in your browser.

How it works

The tool first confirms the CZ prefix, then branches on the length of the body:

Legal entity (8-digit IČO) — multiply the first seven digits by weights 8, 7, 6, 5, 4, 3, 2 and sum them. Take sum mod 11. The check digit is 1 if the remainder is 0, 0 if the remainder is 1, and otherwise 11 - remainder. It must equal the eighth digit.
Natural person (9 or 10 digit rodné číslo) — ten-digit numbers must be divisible by 11 (with the historical pre-1985 final-zero exception); nine-digit numbers are checked for a plausible encoded birth date.

The tool reports the detected type, the rule applied, and (for entities) the computed and provided check digits.

Notes

A valid result confirms the DIČ is well-formed and passes its check rule. It does not prove the entity is currently VAT-registered — confirm that against the EU VIES service. Everything runs locally; your DIČ never leaves your device.