The Korean business registration number, explained
Updated
Every business in Korea has a ten-digit registration number. It appears on invoices, contracts and tax documents, and it is the one piece of information you need to check whether a company you are dealing with actually exists.
The number is written in three blocks: 123-45-67890. Those blocks are not arbitrary. Each carries information, and knowing what it carries lets you spot problems before you query any database.
The three blocks
| Block | Position | What it encodes |
|---|---|---|
| 123 | First three | The tax office that issued the registration |
| 45 | Middle two | Type of entity — individual, corporation, non-profit |
| 67890 | Last five | A serial number, ending in a check digit |
The first block identifies the 세무서, the district tax office where the business first registered. It reflects where the company registered, not necessarily where it operates today, so treat it as a historical fact rather than a current address.
The middle two digits are the useful ones
This block tells you what kind of legal entity you are dealing with. That matters commercially: a sole trader and a corporation carry very different risk, and the number tells you which one signed your contract.
| Code | Entity type |
|---|---|
| 01–79 | Individual, standard VAT-paying business |
| 90–99 | Individual, VAT-exempt business |
| 81, 86, 87, 88 | For-profit corporation — head office |
| 85 | For-profit corporation — branch |
| 82, 83 | Non-profit corporation, or a government or local authority body |
| 89 | Religious organisation that is not incorporated |
| 80 | Unincorporated bodies such as apartment management offices |
The practical use is a sanity check. If a company presents itself as a substantial corporation but its number carries a middle block of 34, you are dealing with an individual sole trader, whatever the letterhead says. That is not fraud in itself — plenty of legitimate businesses are sole traders — but it changes who is liable when things go wrong.
The last digit is a check digit
The final digit is computed from the other nine, so a number containing a typo is almost always detectably invalid. You can rule it out before making any enquiry at all.
The calculation multiplies the first nine digits by a fixed set of weights:
- Multiply each of the first nine digits by 1, 3, 7, 1, 3, 7, 1, 3, 5 in order, and sum the results
- Add the tens digit of the last product — the ninth digit multiplied by five, divided by ten, rounded down
- Subtract the total’s final digit from ten. That result, modulo ten, must equal the tenth digit
A number failing this test cannot exist. If a supplier gives you one, the likeliest explanation is a transcription error rather than deception — but go back and ask, because nothing can be verified until the number is right.
Our checker runs this calculation before querying anything, so an invalid number is rejected instantly.
Check a numberWhat the number does not tell you
The number is an identifier, not a credential. It says nothing about whether the business is solvent, whether it has traded recently, or whether the person handing it to you has any connection to it. For that you need its current status, covered in what a suspended or closed supplier means for your contract.