Japan My Number Validator
Check the check digit of a 12-digit Japanese individual number (My Number) with the official algorithm. 100% local. Built for Japan.
Batch check — paste many, one per line
Validate a Japanese My Number
Enter a 12-digit My Number to verify its check digit. Segmented view, batch CSV, and test-number generation — all locally.
FAQ
What is My Number?
Japan’s 12-digit individual number (マイナンバー). The 12th digit is a check digit computed from the first 11.
How is it validated?
Each of the first 11 digits is multiplied by its official weight, summed, and the remainder mod 11 gives the expected check digit, which is compared.
Can it generate test numbers?
Yes. Generate produces a mathematically valid number marked for testing only — not an assigned My Number.
Is my number uploaded?
No. Validation runs entirely in your browser.
個人番号 (kojin bangō), better known as My Number or マイナンバー, is Japan's 12-digit individual number issued to every resident since notifications began in October 2015 and administered through J-LIS.
The twelfth digit is a check digit: reading the first eleven digits from the right, they are multiplied by the weights 2, 3, 4, 5, 6, 7 and then 2, 3, 4, 5, 6, the products are summed, and the remainder modulo 11 gives the check digit — 11 minus the remainder, or 0 when the remainder is 0 or 1. This tool recomputes that digit locally in your browser, shows the number in segments, and can generate mathematically valid numbers for testing.
Scope and limits: a correct check digit only proves the number is well-formed. There is no public lookup, and under the My Number Act collecting or storing another person's individual number is restricted to specifically permitted purposes such as tax, social security and disaster relief. Treat a real My Number as sensitive data and never paste one into a site you do not trust — this page processes input entirely in your browser and uploads nothing. Last verified: August 2026.
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