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Japan My Number Check

Local processing · not uploaded

Validate Japanese Individual Numbers (My Number) online: 12 digits — the first 11 are the body and the 12th is a check digit verified by the official weighted mod-11 algorithm.

Sample (click to fill): 123456789018

Number—
Check digit—
Validation—

My Number structure and checksum

A Japanese My Number has 12 digits, issued to each resident, with the last digit being a check digit:

Algorithm: for body digit at position n from the right, weight Pn is n+1 for n=1..6 and n−5 for n=7..11. Take Σ(digit×P) mod 11: if the remainder ≤1 the check digit is 0, otherwise 11 − remainder.

How to use

1

Paste or type the ID number above (use the sample to try it out)

2

Click “Check”, and the tool verifies structure and check digit locally in your browser

3

See instantly whether it is valid — nothing is uploaded, no real identity is looked up

✅What this tool does

  • Check the number is exactly 12 digits
  • Weight the first 11 digits by position
  • Verify the 12th check digit by the official mod-11 formula

💡Tips

  • Valid does not mean it exists: only encoding rules and checksum are verified, no personal data is looked up
  • Do not enter other people’s real ID numbers — protect personal privacy
  • Numbers are processed locally in your browser, never uploaded — no signup, no install

🔒 Local processing · numbers not uploaded · only structure and checksum are checked

← Back to Global ID Validator

FAQ

Q1Does a valid result mean it is a real My Number?
No. The tool only checks whether the 12th digit matches the first 11 per the official mod-11 formula. It connects to no government system and looks up no real identity.
Q2Is the number uploaded?
No. All computation runs locally in your browser with JavaScript; the number never leaves your device.
Q3Why do most random 12-digit numbers fail?
Because the 12th digit must exactly equal the check digit computed from the first 11. A random number satisfies this only about 1 in 11 times, so most will fail.