Contribution Share (Kiyo-bun) Calculator | Simulate Your Concrete Inheritance Share

Enter the total estate value and each heir's contribution amount (business labor, nursing care, etc.) to instantly calculate the deemed estate, statutory share, and concrete inheritance share under Japanese Civil Code Article 904-2.

When one of several co-heirs made a special contribution to maintaining or increasing the deceased's estate — through unpaid labor in a family business, financial contributions, or nursing care — Japanese inheritance division deducts that contribution amount from the estate first to calculate a "deemed estate," and the contributing heir then adds the contribution back on top of their statutory share to arrive at their concrete inheritance share (Civil Code Article 904-2). This tool lets you enter the total estate value and each heir's relationship and contribution amount to automatically calculate the deemed estate, statutory share, and concrete share. This is a different system from the "special contribution payment" (Civil Code Article 1050) that non-heir relatives, such as a child's spouse, can claim — if that applies to your case, please use the special contribution payment inheritance tax simulator instead.

Simulate from the estate value, heir composition, and contribution amounts

Tips

  • A "special contribution" typically includes unpaid labor in a family business, financial contributions to the deceased (such as covering medical expenses), nursing care, and property management. Ordinary cohabitation or support within a duty to support generally does not count.
  • If the heirs cannot agree on the contribution amount, any heir can petition the Family Court for mediation or a ruling to determine the contribution share.
  • An ascendant (parent, etc.) is not an heir if the deceased has even one surviving child or a substitute heir. The calculator automatically excludes ascendant rows from the calculation in that case.
  • A contribution share cannot exceed the value of the estate (Civil Code Art. 904-2(3)). This tool shows a warning if it does, but in practice the contribution amount itself needs to be revisited.
  • If a non-heir relative, such as a child's spouse, contributed through nursing care, that falls under the "special contribution payment" (Civil Code Art. 1050) rather than a contribution share. Be careful not to confuse the two.

FAQ

A special benefit reduces the share of an heir who received a lifetime gift or bequest (it is added to the estate before dividing by statutory shares), while a contribution share increases the share of an heir who contributed to maintaining or growing the estate (it is deducted from the estate before dividing, then added back to the contributing heir). The two adjustments run in opposite directions.

The contribution needs to be unpaid or nearly so, and go beyond what would normally be expected. If you received a normal salary while helping the business, or your help stayed within the scope of an ordinary duty to support, it tends to be harder to have it recognized as a special contribution.

In the first instance, all heirs decide it together in the estate division discussion. If they cannot agree, any heir can petition the Family Court for mediation or a ruling on a "proceeding to determine contribution share," and the court will set an amount after considering the circumstances.

A child's spouse is not a statutory heir, so they cannot claim a contribution share directly. Instead, they may be able to claim a "special contribution payment" (Civil Code Art. 1050), introduced by the 2019 reform, from the heirs.
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Side Note — Why a contribution share is deducted upfront

The contribution share system arose from the idea that if one heir made a special contribution to maintaining or growing the deceased's estate, simply splitting the remaining estate equally without accounting for that contribution would be unfair. For example, a child who worked unpaid in the family business for years, compared to a sibling who moved away and never helped, ending up with exactly the same inheritance does not sit well with most people's sense of fairness.

The calculation first deducts the contribution share from the estate to create a "deemed estate," from which each heir's nominal share is calculated according to the statutory share. The contributing heir then adds the deducted contribution back on top of their nominal share. Unlike the advancement of special benefits, which adds an amount to the estate before dividing, contribution share works by setting an amount aside from the estate first.

Japan's 2019 inheritance law reform introduced a new claim called the "special contribution payment" to address a gap: a non-heir relative — typically the spouse of a child who provided nursing care — could not claim a contribution share simply because they were not an heir. A contribution share adjusts an heir's own portion, while a special contribution payment is a separate system letting a non-heir claim money from the heirs.

Disputes over contribution share are often difficult to resolve because it is hard to put a market value on years of unpaid business labor, and Family Court rulings on the amount can vary widely. A simplified simulation like this one is best used as a rough starting point for discussion, not a final answer.

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