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Side Hustle Tax Calculator (Japan)

Calculate the additional tax (income + resident) you owe on top of your main salary, and the real take-home from your side hustle.

Input

Main job: annual gross salary

JPY

Side hustle: annual income (after expenses)

JPY

Side income type

Age group

Estimated Result

Side hustle: real take-home (after extra tax)

398,950JPY

Effective rate vs side income: 79.8%

Main job take-home (baseline): 3,914,149 JPY
Combined income (salary + side): 4,020,000 JPY
Additional income tax: −50,000 JPY
Additional resident tax: −50,000 JPY
Total additional tax burden: 101,050 JPY

* 2026 tax year. Main job calculated using Kyokai Kenpo Tokyo rates. Combined income tax computed and difference vs main-job-only is shown as "additional tax". Misc income under 200,000 JPY is exempt from income tax filing (but resident tax filing required).

FAQ

Q. What is the "200,000 JPY rule"?: If your side income is misc (zassho, 雑所得) and total under 200,000 JPY/year, you don't need to file an income tax return. But you still need to file a resident tax declaration at your municipality.
Q. Misc income vs business income?: Misc: occasional, like Mercari sales or affiliate. Business: continuous and systematic, requires opening declaration. Business gets blue-return deduction up to 650,000 JPY but loses the 200k rule.
Q. Will my employer find out?: Risk is the resident tax going up. Choose "self-payment" (普通徴収) on your tax return so the side income tax bill goes to your home, not deducted from main salary.