Spouse income and your limit

If you are married, your spouse's income can change your furusato nozei donation limit even though the donation itself is made in your name. This is because your limit is tied to your own taxable resident income, and the deductions you are able to claim, including deductions related to your spouse, move that number up or down. Understanding how the spouse deduction works helps explain why the calculator asks about your marital and income situation before showing a result.

Spouse deduction and special spouse deduction (approximate thresholds)

Japan's income tax system offers two related deductions for a lower-earning spouse: the spouse deduction (配偶者控除) and the special spouse deduction (配偶者特別控除). Roughly speaking, if your spouse's employment income is about 1.03 million yen or less in a year (which works out to a total income of around 480,000 yen or less after the employment income deduction), you can claim the full spouse deduction. As your spouse earns more than that, the deduction does not simply disappear. Instead it shifts into the special spouse deduction, which phases down gradually as your spouse's income rises, reaching zero at roughly 2.01 million yen of employment income.

Your own income matters too. The spouse deduction begins to shrink once your own income is relatively high, roughly above 10 million yen of employment income, and it disappears entirely once your income passes the top of that phase-out range.

These thresholds, often called the "income walls," have been adjusted in recent tax reforms and may be revised again. Treat the figures above as approximate and confirm the current year's exact numbers before relying on them for a precise calculation.

Why a spouse deduction lowers your limit

Your furusato nozei limit is calculated from your taxable resident income after deductions. Any deduction that reduces your taxable income, including the spouse deduction or special spouse deduction, also reduces the base your limit is calculated from. In practical terms, this means a single earner who supports a spouse with little or no income will have a smaller furusato nozei limit than an otherwise identical person who claims no spouse deduction at all. The deduction is a genuine tax benefit, but it does shrink the room you have for furusato nozei donations, so it is worth accounting for rather than assuming your limit matches a rough online estimate meant for a single filer.

This same logic applies to other deductions tied to family circumstances, such as those for dependents living abroad, and to income sources that can push your taxable income the other way, such as bonuses and RSUs. All of these factors interact with your limit through the same mechanism: they change your taxable income, and your taxable income drives the calculation.

Dual-income couples: two separate limits

When both spouses have their own income and pay their own taxes, the picture is different. Each spouse has an independent furusato nozei limit based on their own taxable income, and each can make donations up to that personal limit. There is no mechanism to pool the two limits together, and one spouse cannot use the other spouse's unused capacity.

This also means the donation has to be made by, and paid by, the person whose tax bill it is meant to reduce. A donation only counts toward the limit and tax benefit of the person named as the donor and the person who actually pays for it.

Which calculator option to pick

The options in the calculator map directly to the two situations described above:

• Married, spouse income under 1.03 million: choose this if your spouse's employment income is at or below the roughly 1.03 million yen threshold for the full spouse deduction. This option applies the spouse deduction and produces a lower limit than a single-filer estimate would.
• Married, dual income: choose this if both you and your spouse have your own income and neither of you is claiming a full spouse deduction for the other. No spouse deduction is applied, and each partner should run the calculator separately using their own income to get their own limit.

If your spouse's income falls in the middle range where the special spouse deduction partially applies, the exact deduction amount depends on both incomes and the current year's thresholds, so treat any calculator estimate in that range as approximate rather than exact.