Every person registered as a resident of Japan has a My Number, a 12-digit number that stays with them for life. Foreign nationals receive one when they register their address with a municipality after arrival. The number itself is distinct from the My Number card, an optional photo ID card with a chip that holders can use for online government services and, since December 2024, as their health insurance card; new paper health insurance cards are no longer issued.
Employers need the number because it appears on the forms they file: withholding slips, social insurance enrolment and employment insurance notifications. They collect it from each employee, and from dependants listed for tax purposes, and must confirm both the number and the person's identity when they do.
The rules on handling are stricter than for ordinary personal data. A business may collect and keep the number only for the purposes the law allows, must restrict who can see it, must keep it securely and must delete it once it is no longer needed. Leaking it deliberately for improper purposes is a criminal offence.
What it means for a foreign employer
- Collect it at onboarding, for the family too. Missing numbers delay social insurance enrolment and tax filings.
- Keep it out of global HR systems. Storing the number in a worldwide HR platform or emailing it to regional teams creates risk. Restrict it to the Japanese payroll process and the people who run it.
- New arrivals need address registration first. A foreign hire cannot give you a number until they have registered with their municipality, which happens after arrival.
- Do not use it as an employee ID. Using the number for any purpose outside those permitted, such as staff identification, is not allowed.
Sources
- Act on the Use of Numbers to Identify a Specific Individual in Administrative Procedures (My Number Act).
- Personal Information Protection Commission, guidelines for business operators on the handling of specific personal information.
- Digital Agency, guidance on the My Number card as a health insurance card from December 2024.