A furusato nozei simulator gives you a quick estimate of your deduction limit. It’s only as good as the numbers you enter and the cases it covers. Use your withholding slip for the inputs, check the result with last year’s resident tax notice, and donate a little below it.
Key facts (as of October 2026)
- What you need: Last year’s withholding slip (gensen choshuhyo, 源泉徴収票), and ideally your resident tax notice.
- Rakuten’s simulator: The simple version is for salaried workers. (Rakuten)
- The result: An estimate, not a guarantee. Leave a margin.
- Above the limit: You still get a deduction, but you pay more than ¥2,000 in total.
What does a simulator actually calculate?
It estimates the donation where your real cost stays at ¥2,000. That point is your deduction limit.
The limit comes from MIC’s formula. The resident tax special part is capped at 20% of your resident tax income-based part (shotokuwari, 所得割額). (MIC) Your income tax rate also matters.
A simulator doesn’t know your resident tax. It estimates it from your salary, family, and any deductions you enter. Every gap in those inputs shows up in the result.
What do you need before you start?
Have last year’s withholding slip in front of you. Your employer gives it to you.
A detailed simulator usually asks for numbers like these. The exact field names differ by simulator, so match them carefully.
| On your withholding slip | What it means |
|---|---|
| 支払金額 | Total salary paid in the year |
| 給与所得控除後の金額 | Salary after the employment income deduction |
| 所得控除の額の合計額 | Total of your income deductions |
| 源泉徴収税額 | Income tax withheld |
A simple simulator asks for less, often your salary and family. That’s faster, but it can miss things. See the cases below.
How do you use Rakuten’s simulator?
Rakuten Furusato Nozei has a simulator at this address: event.rakuten.co.jp/furusato/guide/simulation/. Its simple version is for salaried workers. (Rakuten)
The page is in Japanese. Your browser’s translate feature works for the labels.
- Open the simulator page.
- Choose the simple version if you are a salaried worker.
- Enter your salary and family details from the withholding slip.
- Note the result, then check it with the formula below.
If you have income other than salary, the simple version isn’t built for you. For donating on Rakuten, see How to Use Rakuten Furusato Nozei in English.
How do you double-check the result?
Use last year’s resident tax notice (juminzei kettei tsuchisho, 住民税決定通知書). It shows your actual income-based resident tax, so you don’t need to estimate it.
Limit ≈ (Resident tax income-based part × 20%) ÷ (90% − income tax rate × 1.021) + ¥2,000
This formula comes from MIC’s deduction rules. The 1.021 adds the special reconstruction income tax, which applies to donations through 2037. (MIC)
For example, an income-based part of ¥2,000,000 and a 33% rate gives about ¥712,000. If the simulator shows something very different, find out why before you donate. For the full method and rate table, see Furusato Nozei Limit.
When can a simple simulator be off?
A simple simulator works best for one salary, one employer, and no unusual deductions. These cases are where it can miss.
Your income this year is different from last year
Your limit depends on this year’s income. Resident tax is based on the previous year’s income. (MIC) If you got a raise, changed jobs, or took leave, last year’s numbers won’t match.
You have a high income tax rate
The formula depends on your income tax rate. MIC notes that the special part uses a rate based on your resident tax income. It can differ slightly from your actual income tax rate. (MIC)
If your salary is over ¥20 million, you must file a tax return. (NTA) At very high incomes, a ¥1.93 million cap also applies from 2027 donations. See The ¥1.93 Million Furusato Nozei Cap from 2027.
You have large other deductions
The limit is based on your actual resident tax. A simple simulator can only reflect the deductions it asks about. Anything else isn’t in its estimate.
Large medical expenses are one example. If you claim them, you file a tax return, so you can’t use the one-stop exception. (Takasaki City)
You contribute to iDeCo
iDeCo contributions are fully deductible from your income. (iDeCo official site) A simulator that asks only for salary and family can’t see them. Enter them if it asks, or use the resident tax check above.
You have income other than salary
Some foreign residents also have income such as RSUs (stock compensation) or side income. A simple simulator for salaried workers may not include income other than salary.
If you have one employer and your income other than salary is over ¥200,000, you must file a tax return. (NTA) For how your own income is taxed, ask a tax professional.
| Your situation | Simple simulator | Better check |
|---|---|---|
| One salary, same as last year | Usually fine | Resident tax formula |
| Income changed this year | May be off | Adjust for this year, leave a margin |
| Salary over ¥20 million | May be off | Formula, then a professional if unsure |
| iDeCo or large deductions | May be off | Resident tax formula |
| RSUs or side income | May not include it | Ask a tax professional |
How much margin should you leave?
There’s no official number. The formula and simulators both give estimates. MIC itself notes the rate used can differ slightly. (MIC)
Going a little over isn’t a disaster. The basic part and the income tax part continue above the limit. (MIC) You just pay more than ¥2,000 on the extra amount.
If your income this year is uncertain, donate part now. Donate the rest in December, once your bonus is known.
What should you do next?
- Get last year’s withholding slip and resident tax notice.
- Run a simulator, then check the result with the formula.
- If the two numbers differ a lot, find the reason first.
- Donate a little below the lower number.
New to furusato nozei? Start with Furusato Nozei Guide.
FAQ
Which is more accurate, a simulator or the formula?
The formula uses your actual resident tax, so it’s often the better check. Both are estimates. (MIC)
I arrived in Japan last year. Can I use the formula?
Your resident tax notice may not reflect a full year of income. Resident tax is based on the previous year’s income. (MIC) A simulator with this year’s expected salary may suit you better.
Do different portals give different results?
They can, because each simulator asks different questions. Check any result with the formula.
Is Rakuten’s simulator only for Rakuten donations?
The simulator estimates your limit. The limit itself is the same whichever portal you use.
Can I use a simulator if I’m self-employed?
Rakuten’s simple version is for salaried workers. (Rakuten) Use the formula with your resident tax notice instead.
Does my spouse need a separate simulation?
Yes. Each taxpayer has their own limit based on their own taxes.
This article is general information, not tax advice. Simulators and the formula give estimates, not exact figures. Information is as of October 2026. Sources: MIC: Tax deductions, Rakuten Furusato Nozei guide, NTA: Who must file.