It's the sub's favorite time of year: tax return filing season! Whether you're filing a Japanese tax return for the first time or you're an e-Tax power user who made 117 furusato nozei donations, this thread is the place to get the resources and answers you need.

How to file

For most people, the simplest way to prepare an income tax return is to use the NTA’s tax return preparation site. You can use the site regardless of whether you intend to submit your return electronically or on-paper. (Though see here for the list of people who are not allowed to use the site. Those people must either use the downloadable e-Tax software or—in some cases—submit a handwritten return using the forms here.)

To submit your tax return electronically, you will need either (1) a MyNumber Card with an unexpired digital certificate or (2) a User ID/Password issued by your local NTA office (though the NTA has stopped issuing User IDs so you can only use this method if you already have one).

To submit using a MyNumber Card, you will also need a smartphone with the MynaPortal app (see a list of compatible phones here) or an IC card reader (see a list of compatible card readers here). Furthermore, you will need to know both the 4-digit PIN (利用者証明用電子証明書) and the alphanumeric password (署名用電子証明書) associated with your card. If you have forgotten either the PIN or the password, you can reset it at a convenience store (see here). If you have forgotten both, you will need to visit a municipal office.

The vast majority of people who file Japanese tax returns do not need to visit an NTA office. But if you are determined to talk to the NTA in person, see here for a list of consultation venues and see here for information about how to make a reservation. It is also worth being aware that—while NTA staff are helpful and knowledgeable in general—they are very busy during filing season and may not have the time to give you comprehensive or accurate advice.

The NTA has published guides to using the tax return preparation site (mobile version) in six foreign languages (including English), though the guides only cover a limited set of circumstances (salaried employee, no residential mortgage, etc.). The site itself is also fairly compatible with translation browser extensions and many people with minimal Japanese-language ability are able to use it.

Documents and data

The list of documents that must normally be attached to an income tax return is here, but people who submit their return electronically are exempt from providing many of them (see here for the full list of exemptions). In any event, if you use the tax return preparation site, it will tell you which documents (if any) you are required to submit.

If you have a MyNumber Card and compatible smartphone (or IC card reader), you can also link the NTA's tax return preparation site to MynaPortal, which will enable the site to automatically populate your tax return using data associated with your MyNumber Card. Specifically, the site can pull the following types of data from MynaPortal:

• Annual withholding summary for employees (as long as your employer submitted it electronically and the name/address/date-of-birth on it match your MyNumber Card exactly)
• Annual withholding summary for pension recipients (as long as the payer is on this list)
• Annual transaction summary for designated investment accounts (as long as the brokerage is on this list)
• Annual medical expenses summary issued by health insurance providers including expenses incurred by family members
• Annual furusato nozei donation summary (as long as the donation was made via a platform on this list)
• National pension contribution history
• iDeCo contribution history
• Deductible life insurance/earthquake insurance premiums paid (as long as the insurer is on this list)
• Outstanding residential mortgage balance (if you have a mortgage from the Housing Finance Agency, such as Flat 35)

Note that different institutions make the above information available at different times. Medical expenses summaries, for example, will not be available until February 9 at the earliest. Some other types of information may not be available until mid-February.

Effect of 2025 tax reforms

As explained at length in this post from August, the government made some significant changes to the Income Tax Law last March, with the changes applying to the whole 2025 tax year. The changes primarily affect people with working dependents (especially dependents aged 19-22).

Perennial talking points

Business income vs. miscellaneous (business) income

This distinction affects everyone who performs work as anything other than an employee. See this post for an explanation of the NTA's current guidelines. If you have side income to declare on an income tax return, it is critical to understand how the side income should be classified.

Choice of dividend taxation method

This is the question of whether recipients of dividend income derived from listed/publicly-offered shares/funds should (1) subject their dividend income to taxation at marginal rates (after being combined with their other income), (2) subject their dividend income to taxation at flat rates (15.315% income tax and 5% residence tax), or (3) exercise their right to not declare the dividend income on their income tax return (only available if Japanese tax was withheld from the dividend when it was paid).

There are a range of factors affecting this decision, including:

• dividend income taxed at marginal rates attracts residence tax of 10% (higher than the 5% applicable to dividend income subject to flat-rate taxation);
• the dividend tax credit is only available with respect to dividends taxed at marginal rates (but the tax credit is only available to people holding shares in Japanese companies or funds that have significant holdings in Japanese companies);
• if the taxpayer is enrolled in National Health Insurance, dividend income declared on an income tax return (regardless of the method of taxation) will increase their NHI premium (unless the taxpayer is already paying the maximum premium);
• it is not possible to claim a foreign tax credit with respect to foreign tax paid on a dividend unless the dividend is declared on an income tax return;
• in order for dividends to be offset by capital losses derived from the sale of listed shares, the dividends must be declared on a tax return and subjected to flat-rate taxation (unless the dividends and the capital loss were handled within the same withholding-type designated account, in which case declaration on an income tax return is not necessary); and
• in order for dividends to be offset by losses derived from real estate ownership or business activities, the dividends must be subject to marginal rates taxation.

One common answer to the question of which taxation method to choose is to simply prepare your income tax return in three different ways (marginal rates, flat rates, and—if eligible—non-declaration), comparing your income tax liability in each scenario. However, some factors (such as the difference in residence tax, and the effect on NHI premiums) will not be captured by that process, so it is important to remember to account for such factors separately.

Useful links

• the NTA's tax return information site;
• the NTA's English-language guide to income tax returns;
• the NTA's foreign-language guides to using the tax return preparation site
• information from the NTA about when employees are required to submit an income tax return;
• a guide to claiming a foreign tax credit;
• a page from the wiki summarizing taxation rights under some of Japan's major tax treaties;
• last year’s tax return questions thread.

As always, discussions in this forum are not a substitute for professional advice, and users are encouraged to keep their questions broad, so as to avoid violating rule 3 (don’t ask for professional advice).