About

Tedorinet is a Japanese take-home pay calculator built around three facts that most calculators skip or get wrong: social insurance is levied on a grade rather than your salary, resident tax is a separate tax on the prior year’s income, and FY2026 adds a brand-new child-care support levy. Getting those three right is the whole point of the project.

How it is built

The calculator works annually — the only correct basis for the deductions and the prior-year resident tax — and shows the monthly figure as annual ÷ 12. It computes social insurance off the standard-monthly-remuneration grade, income tax through the employment-income and basic deductions and the quick-calc table plus the reconstruction surtax, and resident tax as a separate, clearly-labelled prior-year estimate rather than a this-month withholding. Every result states which tax year, which FY rate set, and which prefecture it used, because in Japan those three clocks genuinely differ.

Where the figures come from

The values are drawn from the primary sources and cited to them: the National Tax Agency (国税庁 / NTA) for income tax and the deductions, the Japan Pension Service (日本年金機構) and Kyōkai Kenpo (全国健康保険協会) for social insurance, the Ministry of Health, Labour and Welfare (厚生労働省) for employment insurance and the minimum wage, and the Ministry of Internal Affairs and Communications (総務省) for resident tax. Prefecture health rates come from Kyōkai Kenpo’s own rate tables.

Publisher

Our honesty posture

No figure on this site carries a sign-off. That matters, so we state it plainly: the site never claims to have “verified” a number. It cites the primary sources; the operator is the reviewer of record, and no figure here has been through that review. Where a value rests on paraphrase rather than a verbatim quote — a couple of the deduction age bands, the lowest-rate prefecture, the exact adjustment credit — we say so and hedge rather than assert precision.

We also disclose the model’s simplifications rather than bury them: the annual gross is treated as twelve equal months, bonuses are not modelled separately, the employment-income deduction uses a smooth approximation of the statutory step table, and the resident-tax line is an estimate on current income used as a proxy for the prior year. None of these is hidden; each is stated where it bites. Unsigned as they are, treat the whole calculator as a well-sourced illustration, not advice.