BTSDB Guide · Business — reading the 10 digits like a local
Every registered business in Korea — from Samsung to a one-person
online shop — has a unique 10-digit 사업자등록번호 (business registration number), written as
123-45-67890. It's the closest thing Korea has to a public company ID, and the digits aren't
random: they tell you who issued it, what kind of entity you're dealing with, and whether the number itself
is even plausible.
Anatomy of the number
First 3 digits
Code of the tax office that issued the registration. Historically
geographic, though today it doesn't always match the company's current location.
Middle 2 digits
The most useful part — an entity-type code that
reveals whether you're dealing with an individual or a corporation (see table below).
Last 5 digits
A serial number, ending with a check digit computed
from the first nine digits. Typos and fabricated numbers usually fail this checksum.
Reading the middle two digits
01–79
Individual business (sole proprietor), VAT-taxable
81, 86, 87, 88
For-profit corporation, head office — the typical
주식회사 (stock company)
Example: 120-88-00767 (Coupang) has "88" in the
middle — a for-profit corporation's head office. A supplier claiming to be a large corporation whose number
shows 01–79 is a sole proprietor, which changes your contract counterparty and risk profile.
Why the checksum matters to you
The final digit is derived mathematically from the first nine
(weights 1-3-7-1-3-7-1-3-5, plus a correction term). Around 90% of random or mistyped 10-digit strings fail
it. The BTSDB checker validates the checksum instantly and then confirms with
the National Tax Service whether the number is actually registered — passing the checksum alone doesn't mean
the business exists.
Where to find the number: Korean law requires online sellers to display it in the site footer.
On invoices and contracts it appears near the company seal. On business cards it's often labeled
"사업자등록번호" or "Biz Reg. No."