What the middle digits in a Korean business number mean

The 10-digit Korean business registration number isn't random. The middle two digits encode the entity type, the last digit is a checksum, and you can validate fake numbers without calling anyone.

Middle two digits → entity type

• 01–79: Individual business (general taxpayer)
• 80: Non-profit HQ (individual representative)
• 81, 86–88: For-profit corporation HQ
• 82: Non-profit corporation HQ/branch
• 83: State/local government
• 84: Foreign corporation HQ/branch
• 85: For-profit corporation branch
• 89: Non-business
• 90–99: VAT-exempt individual business

Last digit = checksum

Weights 1, 3, 7, 1, 3, 7, 1, 3, 5 applied to the first 9 digits. The 9th digit also adds the tens-place of its ×5 result. Then checksum = (10 - sum % 10) % 10.

Bottom line

Checksum passing = format is valid, not that the business is active. Use the validator first, then check Hometax for active status.