Format check only (digit count + check digit). This does not look up the National Tax Agency register, so it cannot confirm whether a number is actually registered.
A checker for the Japanese qualified-invoice registration number ("invoice number": the letter T followed by 13 digits). Enter a number and it verifies (1) that it starts with T, (2) that it has 13 digits, and (3) that the check digit (the first of the 13 digits, computed from the other 12 by the same formula as the corporate number / hojin bango) is consistent. Put one number per line to validate a whole list at once — each row gets an OK/NG verdict and a reason (wrong length, check-digit mismatch, missing T). Full-width digits, hyphens and spaces are normalized automatically before checking. Copy the results as TSV to paste straight into Excel or Google Sheets. This is a format check only (digit count + check digit); it does not query the National Tax Agency register, so it cannot confirm whether a number is actually registered or show the business name — use the NTA public site for that. Numbers are never uploaded or stored; everything runs in your browser.
How to use
- Paste the registration number (T + 13 digits) into the box. For several, put one per line.
- Each line gets an OK/NG verdict (digit count + check digit) with a reason, instantly.
- Optionally hit "Copy (TSV)" to paste the results into Excel or Google Sheets.
FAQ
How do I check whether an invoice number is valid?
Enter the number and it checks that it starts with T, has 13 digits, and that the check digit (first of the 13, derived from the other 12) is consistent — showing OK/NG with a reason. Full-width digits and hyphens are normalized first. This is a format check; whether the number is actually registered must be confirmed on the National Tax Agency public site.
How many digits is the registration number, and what is the check digit?
A qualified-invoice registration number is T plus 13 digits. The first of the 13 digits is a check digit computed from the remaining 12 by a fixed formula (the same one used for the corporate number). Even with 13 digits, if that check digit does not match, the number is likely mistyped.
Can I check many numbers at once?
Yes. Put one number per line and each is validated separately into a list of OK/NG verdicts. Copy the results as TSV to paste into Excel or Google Sheets — handy for format-checking a list of suppliers.
Does it confirm registration or the business name? Is my input stored?
No. It only validates the format (digit count and check digit); it does not query the register, so it cannot confirm registration or show the business name — use the National Tax Agency public site for that. Numbers entered are never uploaded or stored; everything runs in your browser.