Business number checker
Check the check digit of a Korean business or corporate registration number and see what each part means.
Business registration number
Hyphens are optional. The number is checked inside this browser and is never sent anywhere.
A correct check digit only means the number is well formed. It does not show whether the business is registered, or whether it is open, suspended or closed. Check that on Hometax.
Corporate registration number
Enter the corporate registration number shown on the company register or the business registration certificate. Do not enter a resident registration number.
How the numbers are built
- A business registration number has 10 digits: 3 digits, a 2 digit type code (individual or corporation), a 4 digit serial number and a check digit (National Tax Service and the 110 government call center).
- Check digit: multiply the first 9 digits by 1, 3, 7, 1, 3, 7, 1, 3, 5 and add them up, then add the tens digit of the 9th digit times 5. The check digit is 10 minus the last digit of the sum (0 if the result is 10).
- The first 3 digits do not tell you the current tax office, so this tool does not name one.
- A corporate registration number is given by the court registry when the corporation is registered: a 4 digit registry office code, a 2 digit corporation type code and a serial number (Supreme Court Rules on registration numbers for corporations, article 2).
- Numbers given until 30 January 2025 end with a 6 digit serial and a check digit: multiply the first 12 digits by 1 and 2 in turn, add them up, and take 10 minus the last digit of the sum (0 if the result is 10). From 31 January 2025 the serial has 7 digits and there is no check digit.
Middle two digits of the business registration number
| Digits | Type |
|---|---|
| 01~79 | Individual business, VAT taxable (general or simplified taxpayer) |
| 90~99 | Individual business, VAT exempt |
| 81, 86, 87, 88 | Head office of a for-profit corporation |
| 85 | Branch of a for-profit corporation |
| 82 | Non-profit corporation, head office or branch (including groups treated as corporations) |
| 83 | State, local government or local government association |
| 84 | Foreign corporation: head office, branch or liaison office |
| 80 | Unincorporated group such as an apartment management office, or a multi-level marketing seller |
| 89 | Religious group that is not a corporation |
This tool only checks the shape of a number. The Hometax lookup is the official record of a business's status. It is a guide, not legal or tax advice.
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