Business Registration Checker - 사업자등록번호 확인
Validate Korean business registration numbers (사업자등록번호) using the official checksum algorithm. Offline validation — no API calls.
What Is a Business Registration Number?
A Korean Business Registration Number (사업자등록번호) is a unique 10-digit identifier assigned by the National Tax Service (NTS) to every registered business in South Korea. The format is XXX-XX-XXXXX, where the first 3 digits indicate the regional tax office, the next 2 indicate the business type, and the last 5 include a serial number with a check digit. This tool validates the mathematical checksum to verify the format is correct.
How to Validate a Business Registration Number
- Enter Number — Type or paste a 10-digit business registration number (hyphens are auto-added)
- Click Validate — The checksum algorithm runs instantly
- View Result — See if the number is valid, along with region and business type info
- Batch Mode — Paste multiple numbers (one per line) to validate them all at once
Why Use This Tool?
- Instant Validation — Check format validity without visiting the NTS website
- Batch Processing — Validate dozens of numbers at once
- Region Detection — Identifies the regional tax office from the first 3 digits
- Type Detection — Determines individual vs. corporate business type
- Auto-Format — Automatically adds hyphens to raw 10-digit numbers
- Privacy — offline; no data sent to any server
Offline Validation vs NTS API Check
| Feature | This Tool (Offline) | NTS API Check |
|---|---|---|
| Speed | Instant | 1-3 seconds |
| Format Validation | Yes | Yes |
| Business Exists? | No | Yes |
| Business Status | No | Yes (active/closed) |
| Batch Support | Yes | Limited |
| Privacy | local | Server query |
FAQ
Can this tool confirm a business actually exists?
No. This tool only validates the mathematical checksum of the number format. To verify actual business registration status, use the NTS HomeTax (홈택스) service.
What is the checksum algorithm?
The algorithm uses weights [1,3,7,1,3,7,1,3,5] multiplied against the first 9 digits, with a special calculation for the 9th digit. The check digit (10th) must match the computed value.
What do the first 3 digits mean?
They represent the regional tax office code. For example, 101-121 is Seoul, 131-138 is Busan, 201-212 is Gyeonggi, etc.
What do digits 4-5 indicate?
Digits 4-5 indicate the business type: 01-79 for individual businesses (개인사업자) and 80-89 for corporate businesses (법인사업자).
Is this tool free to use?
Yes, completely free with no limits. All processing happens in your browser.