Starting in October 2015, municipalities began mailing all foreign residents in Japan information about a new Individual Number system nicknamed “My Number,” or 「個人番号」or「マイナンバー」. Under this system, your Social Security and Tax Number (which is the Individual Number) will be used by various agencies for tax purposes, pension and welfare benefits. This 12-digit number is unique to you and is assigned to you for life. The envelope mailed to you will contain a notification card that has your Individual Number on it. Please keep it in a safe place and do not tell it to anyone unless absolutely necessary (i.e when you employer needs it for tax and social security purposes or to collect pension or welfare benefits).
Additionally, you may apply to have the Individual Number in the form of a plastic card, called an “Individual Number Card,” sent to you. There are several ways you can apply for this card. First, you may request this card by mailing in the form from the “My number” envelope mailed to you. You can also apply online and submit a digital photo. Applying for this card is completely optional.
You will also need this number in order to extend your visa should you stay in Japan longer than your initial visa allows.
For additional information please consult the Kojinbango website.