Japanese corporate number (法人番号) check digit validator
Check whether a 13-digit Japanese corporate number is well-formed.
Type a number and it is checked as you go. The calculation runs in your browser; nothing is sent.
What a corporate number is
A 13-digit number the National Tax Agency assigns to every registered corporation in Japan — 5,827,771 of them as at 2026-08-31. The leading digit is a check digit over the other twelve, so transposed and mistyped digits are caught locally, before you call anything.
How the check digit is computed
check digit = 9 − ((Σ Pn × Qn) mod 9), where Pn is the nth digit counting from the RIGHT of the twelve-digit body, and Qn is 1 for odd n and 2 for even n. Counting from the left instead still produces a plausible digit about one time in nine, which is why that mistake survives testing.
Common questions
How many digits is a Japanese corporate number?
Thirteen. The first is a check digit; the remaining twelve are the body.
Does a valid check digit mean the company exists?
No. It means the number is well-formed. Whether it was ever assigned requires a register lookup — well-formed unassigned numbers are trivial to generate.