Japan Corporate Number Validator

The Japanese corporate number (法人番号) is a 13-digit identifier the National Tax Agency assigns to every company, government body and registered organisation. Unlike the personal My Number, it is public information. Since the qualified-invoice system began, businesses use a T plus their corporate number as their invoice registration number. The leading digit is a check digit, so typos are detectable. This free validator runs the official algorithm.

How it works

The corporate number uses a modulo-9 check digit. The leftmost digit is the check digit; the remaining 12 digits form the base. Number the base digits 1 to 12 starting from the lowest (rightmost) position:

1. Weight each base digit Pn by Qn: Qn = 1 when n is odd, Qn = 2 when n is even.
2. Compute the weighted sum of Pn × Qn.
3. Take that sum modulo 9.
4. The check digit equals 9 - remainder.

The number is valid when this computed check digit equals the actual leading digit. The tool shows the weighted sum, the modulo-9 remainder and the expected check digit so the result is fully transparent.

How it works in practice

If the weighted sum over the 12 base digits gives a remainder of 2 modulo 9, the expected check digit is 9 - 2 = 7, and the corporate number is valid only if its first digit is 7. The alternating 1, 2 weighting from the rightmost base digit catches most single-digit and adjacent-transposition errors.

Tips and notes

• A failed check almost always means a digit was typed wrong or transposed. Re-check all 13 digits against the registry entry.
• To build a qualified-invoice registration number, prefix the validated corporate number with T (for example T followed by the 13 digits).
• A valid checksum confirms internal consistency only. Confirm the organisation exists in the National Tax Agency’s public corporate-number registry. Everything runs locally.