When side income needs a return, the ¥200,000 rule’s real meaning, and business vs miscellaneous income.
Employees with side income may need to file even under the often-cited ¥200,000 line, and whether that income is business or miscellaneous turns mainly on whether you run it like a business and keep books.
A widely repeated rule says employees need not file an income-tax return if their side income is ¥200,000 or less. It is real but narrow: it concerns the national income-tax filing obligation for certain employees whose main job is settled by year-end adjustment, and it is not a tax-free allowance. Even when it applies, your municipality may still require a separate resident-tax declaration on that income — so “under ¥200,000, do nothing” is often wrong.
If your side income is larger, or you have two employers, or you want to claim deductions like medical expenses or a first-year mortgage credit, you file a 確定申告 that includes the side income. When in doubt, filing is the safe default; the resident-tax side in particular is easy to overlook.
How side income is categorized matters a lot. Business income (事業所得) can use the blue return, its up-to-¥650,000 deduction, and loss offset against other income; miscellaneous income (雑所得) cannot. Following the NTA’s clarification, the deciding factor is whether the activity is run as a business by social norms — continuity, scale, effort, and above all keeping proper books and evidence. Records generally point to business income; their absence, or very small casual revenue, points to miscellaneous.
So if you intend your side work to be a real business, treat it like one from the start: file the opening notification and blue-return application, keep double-entry books in accounting software, and retain contracts and receipts. That both supports business-income treatment and prepares you to go fully independent later.
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Possibly, even under the often-cited ¥200,000 line. That figure is a national income-tax filing-obligation rule for certain employees settled by year-end adjustment — not a tax-free allowance — and a separate resident-tax declaration to your municipality can still be required. Whether the income is business income (which unlocks the blue return and loss offset) or miscellaneous income depends mainly on running the activity like a business and keeping proper books. If you intend it to be a real business, file the opening notification and keep double-entry records from the start.
File a notification of business opening (開業届) with your local tax office within about a month of starting — it is free and short. At the same time, file the blue-return application (青色申告承認申請書) to unlock the up-to-¥650,000 deduction. You keep your existing visa status if it permits the work; some visa types need permission for self-employment, so check your residence status first.