Business Number Checksum and Formatting
Test whether the final digit matches the checksum derived from earlier digits. No National Tax Service existence or closure-status lookup occurs, so passing does not certify a business or transaction safety.
- Runs in your browser
- Nothing is uploaded
- No signup; device limits apply
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How to use this tool
Enter the number with or without hyphens. Non-digits are removed before the ten-digit check; inspect the normalised output to ensure cleaning has not produced an unintended sequence.
Results and examples
Passing means the weighted checksum agrees. Unregistered sequences can also pass mathematically, so contracts and tax-document checks still require the appropriate official lookup.
Worked example
For the first nine digits 123456789, this algorithm gives check digit 1 and formats 123-45-67891; this is not an example of a verified business.
Limitations
- Name, representative, address and operating status are not retrieved.
- Checksum success does not establish authenticity or trustworthiness.
Fields
| Field | Guidance and constraints |
|---|---|
| 10-digit business registration number | Check the unit and format displayed beside this field. |
Data handling
Processing stays in the current browser tab; the site does not upload tool input for the calculation itself.
Sources
Frequently asked questions
Does passing mean the business exists?
No. Only mathematical validation is performed.
Must I remove hyphens first?
No, but review the normalised digits after automatic cleaning.
Related tools
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