Business Registration Number Validator
Checks the 10-digit check sum of a Korean business number and can bulk-validate a pasted column.
A Korean business registration number carries a check digit, so a mistyped one can be caught before it goes onto an invoice or into an accounting system. This checks that digit — over a single number, or over a whole column pasted out of a spreadsheet.
사업자등록번호 (business registration number)
Format valid
Category
For-profit corporation (head office)
The check
| Position | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |
|---|---|---|---|---|---|---|---|---|---|
| Digit | 1 | 2 | 4 | 8 | 1 | 0 | 0 | 9 | 9 |
| Weight | ×1 | ×3 | ×7 | ×1 | ×3 | ×7 | ×1 | ×3 | ×5 |
| Product | 1 | 6 | 28 | 8 | 3 | 0 | 0 | 27 | 45 |
- Weighted sum
- 118
- Ninth-digit carry
- ⌊9 × 5 ÷ 10⌋ = 4
- Total
- 122
- Check digit
- (10 − 122 mod 10) mod 10 = 8 · entered 8
The weights are 1,3,7,1,3,7,1,3,5. The ninth digit is multiplied by 5 and the tens digit of that product is added once more — that carry is zero only for a ninth digit of 0 or 1, so skipping it changes the verdict on eight numbers in ten.
How to use it
Paste the number, or the column
Hyphens and spaces are ignored. A pasted list is checked line by line, so a supplier table can go in whole.
Read the middle two digits
They are the 구분코드: which range a number falls in distinguishes an individual trader from a corporation from a non-profit. It is often the fastest way to see that a number belongs to a different kind of entity than expected.
Export the failures
The result table separates valid from invalid, so a bulk check is worth running over a contact list once before the numbers are used anywhere.
Common questions
Does a valid number mean the business exists?
No. This checks the number’s internal arithmetic only. Whether the business is registered, still trading, or suspended is a lookup against 국세청 홈택스, which this tool does not perform.
Can it check a corporate registration number too?
The 13-digit 법인등록번호 is a different number with a different rule and is not what this validates. A corporation also has a 10-digit 사업자등록번호, and that is the one to paste here.
Is anything sent anywhere?
No. The check is arithmetic and runs in your browser, so a customer list pasted here does not leave the tab.
Feed it from
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