A REGON is the statistical identification number the Polish Central Statistical Office (GUS) assigns to businesses and their local units. It comes in two lengths: a 9-digit number for a legal entity and a 14-digit number for a local unit. This free validator detects the variant and runs the matching check-digit algorithm in your browser.
How it works
Both forms use a weighted modulo-11 check digit, with one twist: if the modulo result is 10, the check digit is treated as 0.
- 9-digit entity — multiply the first 8 digits by weights 8, 9, 2, 3, 4, 5, 6, 7, sum them, take modulo 11 (10 becomes 0), and compare against the 9th digit.
- 14-digit local unit — first confirm the embedded 9-digit core is valid, then multiply the first 13 digits by weights 2, 4, 8, 5, 0, 9, 7, 3, 6, 1, 2, 4, 8, take modulo 11 (10 becomes 0), and compare against the 14th digit.
The tool reports both the embedded 9-digit core result and the variant-specific check digit so you can see exactly where a number passed or failed.
Example
For a 9-digit REGON the last digit is the check digit. Apply the 8, 9, 2, 3, 4, 5, 6, 7 weights to the first eight digits, sum, take modulo 11, map a remainder of 10 to 0, and the result must equal the ninth digit.
Notes
A valid check digit confirms the REGON is well-formed, not that the entity exists or is active. To confirm a business, query the official GUS REGON registry. Everything here runs locally — your REGON never leaves your device.