Side income is taxed on top of your salary, at your marginal rate — not from zero. Enter both to see the real extra cost, and whether you need to file.
Fill in the fields, press Calculate, and read the breakdown. Every field has a sensible default, so you can start with an estimate and refine it.
If you're a company employee whose salary already goes through nenmatsu chosei (year-end adjustment) with one employer, and your side income — after expenses — is ¥200,000 or less for the year, you don't have to file a kakutei shinkoku (final tax return) for national income tax. This is the rule most people have heard of.
What catches people out: this only exempts you from filing for income tax. Resident tax has no such exemption — you're still required to report that income to your municipality, usually through a separate jūminzei shinkoku (resident tax return), even when your side income is under ¥200,000. In practice, filing the kakutei shinkoku anyway (even when not required) covers both at once, since the tax office forwards the data to your municipality automatically.
Side income doesn't get its own tax bracket — it's added on top of your salary's taxable income, so it's taxed at your marginal rate, not from zero. If your salary already puts you in the 20% bracket, your side income is taxed at 20% (plus resident tax), not the 5% a low earner would pay on the same amount.
Most side income counted this way is zatsu shotoku (miscellaneous income) — freelance platforms, occasional consulting, content creation and similar. If you've registered it as a real business and file with the aoiro shinkoku (blue form), you may qualify for a deduction of up to ¥650,000 that this calculator doesn't include.
A single company employee under 40 with no dependents, using the Tokyo health insurance rate.
| Side job net income | Additional tax | Filing required? |
|---|---|---|
| ¥100,000 | ¥20,000 | Income tax: no |
| ¥300,000 | ¥61,000 | Income tax: yes |
| ¥500,000 | ¥101,000 | Income tax: yes |
| ¥1,000,000 | ¥202,000 | Income tax: yes |
Figures come from the calculator above and are rounded. Resident tax reporting applies regardless of the income tax filing requirement.
You're exempt from filing a kakutei shinkoku for income tax, but you're still expected to report the income to your municipality for resident tax — check with your city office on their process, since it's separate from the tax office's system.
Costs directly tied to earning that income: software subscriptions, equipment, a reasonable portion of home internet or a home office if you can justify the split, platform fees, and materials. Personal spending that isn't clearly tied to the work doesn't qualify — keep receipts either way.
Zatsu shotoku (miscellaneous income) is the default for occasional or small-scale side work. Jigyo shotoku (business income) requires a formal business registration (kaigyo todoke) and generally more consistent, substantial activity — but it unlocks the blue-form filing benefits, including loss carry-forward and the up-to-¥650,000 deduction. This calculator assumes miscellaneous income, the more common case.
Kakutei shinkoku for a given year is generally due by March 15 of the following year. Filing late or not at all can add a delinquency tax (entai zei) and, in some cases, a penalty tax on top of what you owed — the amount grows the longer it's outstanding, so filing late is still much better than not filing.
Estimates only. Actual costs vary by contract, city and provider. This site is not financial or tax advice.