Japanese Invoice Registration Number Validator
Batch-validate Japanese qualified invoice registration numbers (T-numbers) for the 2023 Invoice System. Checks syntax, digit count, and check digit locally using the NTA's official algorithm.
Invoice Registration Number (T-Number) Batch Validator
Batch-validate qualified invoice registration numbers (T-numbers). Checks the T prefix, 13-digit length, and check digit locally in your browser using the NTA's official algorithm.
This tool validates the format and checksum of T-numbers locally. To confirm actual registration status, use the NTA verification link shown next to each valid number.
T-Number Format Guide
Structure
T + 13 digits
14 characters total
Example
T8700110005901
NTA's own worked example
Check digit
1st digit of the 13-digit body
9 - weighted digit sum mod 9
Accepted input formats: T1234567890123 · T-123-4567-8901-23 · T 1234567890123 · Ｔ１２３４５６７８９０１２３
Hyphens, spaces, and full-width characters are normalized automatically before validation.
Common Problems
How do I validate a Japanese qualified invoice registration number (T-number)?
A valid T-number is exactly 14 characters: the letter T followed by 13 digits. The first digit of the 13-digit body is a check digit computed from the other 12 using the NTA's official corporate-number algorithm (weighted odd/even position sum, mod 9). Paste the number into this tool to check both the format and the checksum in one step.
What does a check digit mismatch mean for a T-number?
A mismatch means at least one digit in the number is wrong. Common causes are OCR misread characters (0 vs O, 1 vs l, 8 vs B), missing or extra digits when copying from a PDF, and hyphen positions shifting digit groupings. Compare the number against the original source document to find the error.
How do I validate a batch of Japanese T-numbers at once?
Paste all numbers into the textarea, one per line or comma-separated. The tool validates all of them simultaneously and shows a per-number result. You can then copy only the valid numbers as a clean list, saving the manual work of checking each one individually on the NTA portal.
My T-number has full-width digits from an OCR scan. Will this tool handle them?
Yes. Full-width T (Ｔ) and full-width digits (０-９) are automatically converted to half-width before validation. Hyphens and spaces used for readability grouping are also stripped. The normalized form is shown alongside the original so you can verify the conversion was correct.
How do I confirm a T-number is actually registered with the NTA?
After running validation, each number that passes the checksum check gets a link to the NTA's public invoice registration portal (invoice-kohyo.nta.go.jp). That page shows the business name, registration date, and whether the entity is an active qualified invoice issuer. Checksum validation here is a fast first filter — the NTA portal is the authoritative source.
Workflow
What is Japanese Invoice Registration Number Validator?
Japan's 2023 qualified invoice system (適格請求書等保存方式) requires businesses to verify supplier T-numbers before claiming consumption tax deductions. Manually checking each T+13-digit number on the National Tax Agency portal works for a handful of invoices, but becomes impractical when auditing monthly batches of 50 or 100 suppliers.
This tool validates the syntax and check digit of T-numbers locally in the browser, using the exact algorithm the NTA publishes for corporate numbers (法人番号) — sum the 12-digit body's odd and even positions separately, double the even-position sum, add them, and take 9 minus the remainder mod 9. That makes it fast to triage a list and identify likely typos or OCR errors before committing to individual NTA lookups.
How to use Japanese Invoice Registration Number Validator
Paste T-numbers one per line or comma-separated. Full-width characters and hyphens are normalized automatically. Click Validate to see per-number results. Valid numbers include a direct link to the NTA public information portal for official registration verification. Use Copy valid to extract only the passing numbers for your records.
Example
Input batch:
T8700110005901 (the NTA's own worked example from its check-digit spec)
T1234567890123
T9876543210987
Results:
✓ T8700110005901 — Valid (checksum matches)
✗ T1234567890123 — Invalid (check digit mismatch)
✗ T9876543210987 — Invalid (check digit mismatch)Use Cases
1. Auditing invoice batches to catch OCR errors before submitting tax filings.
2. Pre-validating vendor T-numbers collected in spreadsheets before importing to accounting software.
3. Quick triage of a list of new supplier numbers without opening the NTA portal for each one.
4. Identifying registration number formatting issues in legacy procurement systems.
FAQ
Does 'Valid' here confirm the business is actually registered?
No. This tool only checks the format and checksum of the number. A number can pass the checksum check and still not be registered with the NTA. For official registration status, follow the NTA verification link provided for each valid number.
How is the T-number check digit actually calculated?
The first digit after the T prefix is a check digit calculated from the remaining 12 digits using the exact algorithm the NTA publishes for corporate numbers: number the 12 digits from the right (position 1 = rightmost), sum the digits at odd positions, sum the digits at even positions and double that sum, add the two together, and the check digit is 9 minus the remainder of that total mod 9. It catches single-digit transcription errors — if the check digit does not match, the number almost certainly has a typo somewhere.
Is it safe to paste invoice or vendor data here?
Yes. All validation runs in your browser. No data is transmitted to any server. Your vendor lists, T-numbers, and invoice data stay entirely on your machine.