Korean BRN Validator Standard NTS checksum
Validate any Korean Business Registration Number (BRN) in seconds. Checksum + business type auto-detection — no login, no API, runs entirely in your browser.
BRN ≠ Corporate Registration Number — they are different
BRN — Business Registration Number
법인등록번호 — Corporate Registration Number
Show how the checksum is calculated
Multiply the first 9 digits by weights [1,3,7,1,3,7,1,3,5], add floor(d[8] × 5 / 10) as a special correction (Korea-specific), then check that (10 − sum mod 10) mod 10 equals the 10th digit.
Type code reference (digits 4–5)
- 01–79 — Individual taxable business (general/simplified)
- 80 — Multi-level sales / apartment management offices, etc.
- 81 / 86 / 87 / 88 — Profit corporation (HQ)
- 82 — Non-profit corporation (HQ/branch)
- 83 — Government / municipality / public body
- 84 — Foreign corporation (Korean branch / liaison)
- 85 — Profit corporation (branch)
- 89 — Religious organization (non-incorporated)
- 90–99 — Tax-exempt individual business
※ Cross-checked against NTS Q&A, Toss Payments developer center, MoneyPin guide (2026-05).
How the checksum works
- Strip non-digits to get
d[0..9]. - With weights
W = [1, 3, 7, 1, 3, 7, 1, 3, 5], computeS = Σ d[i] × W[i]fori=0..8. - Add Korea-specific correction
floor(d[8] × 5 / 10)toS. Most common implementation bug — easy to miss. - Expected check digit
check = (10 − S mod 10) mod 10. - If
check === d[9], the BRN is format-valid.
Verified sources: lesstif PHP gist (Korean standard), Toss Payments developer center, MoneyPin guide. PHP/JS/Python implementations cross-checked.
FAQ
What is a Korean Business Registration Number (BRN)?
A 10-digit number issued by Korea's National Tax Service when a person or entity registers a business. Format: XXX-XX-XXXXX. Required for tax filings, invoices, and B2B transactions in Korea.
How is the BRN checksum calculated?
Multiply the first 9 digits by weights [1,3,7,1,3,7,1,3,5], then add floor(digit[8] × 5 / 10) as a special correction. Take (10 − sum mod 10) mod 10 — this must equal the 10th digit. Standard NTS algorithm.
Why does my BRN show 'foreign' or 'tax-exempt' type?
The 4th–5th digits classify the business: 84 = foreign corporation (Korean branch/liaison of an overseas entity), 90–99 = tax-exempt individual (e.g., farming, fishing, certain professional services). Foreign residents who register a Korean sole proprietorship typically receive 01–79 (taxable) or 90–99 (tax-exempt).
Does this tool confirm my business is actually active?
No. This tool only validates format (checksum + type code). For active/suspended/closed status, dealer info, or representative name, use Hometax (Korea's official tax portal at hometax.go.kr) or call NTS at 126.
What's the difference between a BRN and a Corporate Registration Number?
BRN (사업자등록번호) is 10 digits, issued by the tax office, used for tax filings and invoices. Corporate Registration Number (법인등록번호) is 13 digits, issued by the Ministry of Justice when a corporation is incorporated, used for legal contracts and registry. They are separate numbers — one entity has both. This tool validates only the 10-digit BRN.