My Number


My Number (マイナンバー), officially "Individual Number" (個人番号 - kojin bangou), is a unique number assigned to every resident of Japan for tax and social security purposes.

The 12-digit My Number also acts as a Tax Identification Number (TIN) internationally[1]. Those with savings or investments outside of Japan will ordinarily be required to declare their residency in Japan and their Japanese TIN.

Mynaportal and taxes

Beginning from the 2021 tax year, much of the data from your Mynaportal account can be passed on to the National Tax Agency's online return-preparation site and automatically used to populate items on an e-Tax return. The government refers to this function as "Identity Linkage" on its English website, and all procedures currently (April 2022) need to be done in Japanese, but the function promises to make filing tax returns significantly less of a burden for those able to file their taxes online.

As long as the service provider has registered (no problem in the case of the national pension and national health insurance), automatic entry has recently been expanded to include information for the following six items on your tax return:

  • Furusato nouzei
  • "Specified" brokerage accounts (kabushiki no tokutei kouza 株式の特定口座)
  • Home loans
  • Life insurance
  • Earthquake insurance
  • Medical-care costs (this makes My Number-based treatment records available beginning from September 2021, and is supposed to be fully functional for 2022 income-tax returns)


  1. Obtain a My Number card and register to use Mynaportal (the card must be used to log in, either from a PC with a connected card reader or a compatible smartphone).
  2. Once logged in to Mynaportal, choose the external site you want to connect to from "motto tsunagaru" (もっとつながる).
  3. Follow the instructions to set up the connection.
  4. From your next login, you will be able to make use of that external site from within Mynaportal.

Advantages for filing taxes

  • Data obtained from your Mynaportal account is automatically entered into your online tax return.
  • Records for the data do not need to be kept by the taxpayer as long as the return is submitted via e-Tax.
  • Identity Linkage is persistent and connections only need to be set up once.
  • The NTA plans to expand the system in due course to pension withholding slips and other tax-related items.

Mynaportal limitations

  • Data is only provided by registered entities (here is the complete list as of April 2022).
  • Data for medical expenses has only recently begun to be made available and may be incomplete.

See Also


Many thanks to the following users for writing this article:

CAM, Adamu, Kuma


  1. Information on Tax Identification Numbers (PDF), The Organisation for Economic Co-operation and Development (OECD)