Good news: if you have one employer and no other income sources, your company's 年末調整 (year-end tax adjustment) handles your income tax filing for you. You do not need to file a 確定申告 unless you want to claim deductions your employer doesn't handle (medical expenses, housing loan deduction for first year, etc.).

Your company's HR will ask you to submit a 給与所得者の扶養控除等申告書 (dependant declaration form) in October/November. Fill it out and return it by their deadline. The company does the rest by December 31.

If you have income from any source other than your primary employer — freelance work, content creation, stock/investment gains, rental income overseas, etc. — and that additional income exceeds ¥200,000 per year, you are required to file a 確定申告.

Your company's 年末調整 only covers your employed income. All other income must be declared separately. Missing this is a common source of tax arrears that surfaces at PR applications.

All freelancers and self-employed persons must file a 確定申告 every year, regardless of income level. There is no 年末調整 equivalent for self-employment. You are responsible for calculating and paying both income tax and住民税 yourself.

Key advantage: Self-employed individuals can deduct business expenses — software subscriptions, home office portion, equipment, professional development. Keeping clean records throughout the year makes filing significantly easier. Use accounting software from day one.

If you worked for more than one employer during the year (including changing jobs mid-year where 年末調整 was not completed at the previous employer), you must file a 確定申告. The second employer's withholding tax is typically at a flat rate that doesn't account for your total annual income — which may result in either underpayment (you owe tax) or overpayment (you get a refund).

If you left your job before December 31 and your employer did not do a 年末調整 (which only happens at year end), your taxes for that year were not fully adjusted. You likely paid too much tax through withholding — filing a 確定申告 will result in a refund.

Additionally: if you were unemployed at year end, you need to ensure your 住民税 is paid directly (it's no longer deducted from payroll). Check with your municipal office for the payment schedule.

Employees earning over ¥20,000,000 gross per year must file a 確定申告 even if they have only one employer and no side income. 年末調整 does not apply above this threshold. Your employer will withhold income tax throughout the year, but the year-end reconciliation must be done by you personally.

Within your first 5 years in Japan: Overseas income is only taxable in Japan if you remit it to Japan. Income left in foreign accounts is generally not taxable here yet.

After 5 continuous years as a tax resident: All worldwide income — including overseas salary, investment income, rental income, dividends — is taxable in Japan. You must declare and pay tax on it via 確定申告. Tax treaty provisions may reduce double taxation if your home country also taxes the same income.

Foreign financial account reporting: if you hold overseas accounts with a total balance exceeding ¥50,000,000 at year end, you must file an overseas financial account report (国外財産調書). Failure to disclose is a serious violation.

Even if you're not required to file, you may want to — because you're leaving money on the table. Deductions your 年末調整 often misses:

医療費控除 (medical expense deduction): If total out-of-pocket medical expenses for your household exceeded ¥100,000 in the year, you can deduct the excess. Dental work, glasses for vision correction (requires doctor's note), hospital visits, and some health products count. Keep all receipts.

ふるさと納税 (hometown tax donation): Donate to any Japanese municipality and receive significant tax credits plus local food/product gifts. Must be filed via 確定申告 or the ワンストップ特例 (one-stop exception) system.

住宅ローン控除 (housing loan deduction): For the first year of a qualifying mortgage, must be filed via 確定申告 (年末調整 handles subsequent years).