INTRODUCTION & SHORT MANUAL
Fuyou no Kabe SimulatorJapan dependant-income thresholds
How much more can I work this year?
From an hourly wage and working hours, it estimates annual income, tax, social insurance and take-home pay, and shows how far you still are from the ¥1.03m, ¥1.06m, ¥1.30m and ¥1.60m thresholds.
Open the service Opens a separate site (a subdomain)
- Service URL
- fuyou.rewrite-co.com
- Languages
- Japanese only (the tool models Japanese rules, so the interface is in Japanese)
- Pricing
- Free. Premium, only if you want to save and compare scenarios: JP ¥980/year (incl. tax).
- Who it is for
- Part-time workers in Japan managing their hours around the dependant thresholds — and their families.
About this service
In Japan, part-time earnings above certain annual thresholds change your tax position or push you out of a family member’s social-insurance coverage. Everyone knows the numbers; almost nobody knows how much room they have left this year, because that depends on their own hourly wage and hours. This tool works that out on one screen.
You enter an hourly wage and your working hours. It returns estimated annual income, the tax and social insurance due, and the resulting take-home pay — plus how much more you can earn before each of the four thresholds (¥1.03m, ¥1.06m, ¥1.30m, ¥1.60m). It also shows what happens to take-home pay if you cross one.
It covers the rules for fiscal years 2024 to 2026. No account, no sign-in: open it and use it. It stays usable for free, and the shareable result URL is free too.
Getting started
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Open the tool
No registration and no sign-in. Use the button on the top page, or go straight to the tool page.
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Enter your wage and hours
Hourly wage, hours per day, days per month. The result updates as you change the numbers, which makes it good for asking “what if I add one day a week?”.
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Look at the remaining headroom
You get the remaining amount for each of the four thresholds. Tax thresholds and social-insurance thresholds mean different things, so check which one actually applies to you.
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Share the result with family
You can generate a URL for the result and discuss the same figures with your employer or your family. This is free.
Pricing and cancellation
The core is free: estimates of take-home pay and remaining headroom, and generating a shareable result URL, all without an account.
Premium (JP ¥980/year, tax included) exists only if you want to save several scenarios and compare them — “as now”, “one more day a week”, “after a pay rise” side by side.
What to know before you start
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These are estimates, not exact figures
They follow the general rules and do not account for your particular situation — your municipality, your health-insurance society’s own criteria, how dependency is assessed, other income. For an exact figure, ask your employer or a tax accountant or labour and social security attorney.
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Tax thresholds and insurance thresholds are different things
The ¥1.03m and ¥1.60m lines are mainly about tax; ¥1.06m and ¥1.30m are mainly about social insurance. Which one you cross changes both how take-home pay moves and who is affected — you or the person claiming you.
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The rules change every year
Fiscal years 2024 to 2026 are covered, but there can be a lag before amendments are reflected. When a decision spans fiscal years, check the current official sources as well.
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Your figures are not stored (on the free tier)
Used for free, your wage and hours are never stored on our servers. Note that generating a share URL encodes those inputs into the URL, so be careful who you send it to.
Frequently asked questions
- Do I need an account?
- No. Open it and use it. An account is only needed for saving scenarios on Premium.
- What is the difference between the ¥1.06m and ¥1.30m lines?
- Both concern social insurance. The ¥1.06m line applies where certain conditions are met, including the size of the employer; the ¥1.30m line relates to whether you remain a dependant. Ask your employer which applies to you.
- Do I always lose money by crossing a threshold?
- No. Take-home pay can dip just after crossing, but it recovers as you earn more. The tool estimates that movement too.
- Does it work for other countries?
- No. It models Japanese tax and social-insurance rules only.
This page explains how the service is used. Where it differs from the Terms of Service or the refund policy, those documents apply.
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