The four bills a sole proprietor pays — income tax, resident tax, pension, and health insurance — and how they connect.
A sole proprietor pays income tax (progressive, national), resident tax (~10%, billed the next year), plus National Pension and National Health Insurance — all on profit after expenses and deductions.
Almost everything you owe is calculated from one number: your business profit, which is revenue minus necessary expenses. From that, personal deductions (the basic deduction, the blue-return special deduction, social-insurance premiums, small-business mutual aid, and iDeCo, among others) are subtracted to reach taxable income. National income tax is charged on that at progressive rates, and local resident tax adds roughly 10% on a similar base.
The two social-insurance bills sit alongside the taxes. National Pension is a flat monthly premium set each year; National Health Insurance is calculated by your municipality from your prior-year income. Because resident tax and health insurance both look back at last year, your bills lag your income — a strong year is followed by higher bills the next, which catches many first-year freelancers off guard.
Three levers do most of the work. First, claim every legitimate business expense with evidence. Second, file a blue return so you can take the special deduction (up to ¥650,000 with double-entry books and e-filing) and carry losses forward. Third, use deductible retirement and pension schemes built for the self-employed — small-business mutual aid, iDeCo, and the National Pension Fund — which cut taxable income while building your own safety net.
Set aside a tax reserve from every payment rather than facing the total at filing. A common rule of thumb is 20–35% of profit across all four bills, rising as income grows because income tax is progressive. Confirm each year’s rates, brackets, and deduction amounts before filing — recent reforms have moved the basic deduction and the income thresholds, so last year’s numbers may be stale.
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A sole proprietor pays national income tax (progressive) and local resident tax (~10%), both on business profit after expenses and deductions, plus National Pension and National Health Insurance premiums that you fund yourself. If your taxable sales pass ¥10 million — or you register for the invoice system — consumption tax is added. Resident tax and health-insurance premiums are based on the prior year, so bills lag income. Confirm current rates and deductions each year, as recent reforms have moved the basic deduction and thresholds.
A common rule of thumb is to reserve 20–35% of profit for income tax, resident tax, national pension, and national health insurance combined — higher as your income rises, because income tax is progressive. Remember resident tax and health-insurance premiums are billed based on the prior year, so your bills lag your income. Set the reserve aside in a separate account each month rather than facing it all at filing time.
As a sole proprietor you generally enroll in National Health Insurance (国民健康保険) and the National Pension (国民年金), and you pay both yourself — there is no employer split. National Pension is a flat monthly amount; National Health Insurance premiums are income-based and billed by your municipality. You can add optional coverage (e.g. the national pension fund, iDeCo, or income-protection insurance) to close gaps. Budget these into your tax reserve.