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.

Last updated: 2026-10-17

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

What this contribution share calculator does

Enter the total value of the estate and the contribution claimed by each heir, and this tool works out the notional estate under article 904-2 of the Japanese Civil Code, divides it by the statutory shares and returns the contribution to the heir who made it, giving each person's concrete share as a figure.

The first thing to settle is that the ground for a contribution claim is far narrower than most people assume. The provision requires a special contribution: care and help of the kind ordinarily expected between parent and child or between spouses does not qualify. Living in the same house and taking on the housework, or calling in regularly to help with care, is generally not enough in practice. What tends to succeed is the contribution that translates into money preserved or added to the estate — working in the family business for years without pay, or providing unpaid the nursing that would otherwise have had to be bought in.

Second, only an heir can claim a contribution share. A relative who is not an heir — a son's wife, most typically — cannot be a party to such a claim however much of the care they carried. Since July 2019 a separate regime, the special contribution payment, addresses that imbalance by allowing such a relative to claim money from the heirs. The two regimes differ in whom you claim against and by when, so establish which one applies before anything else.

Finally, the amount is settled first by agreement among all the heirs. Where no agreement is reached, the family court decides by conciliation or adjudication, and there the records that evidence the contribution carry the weight — the reality of the work done, receipts for expenditure, a care diary. Use this estimate as a starting point for the discussion and take the claim itself to a lawyer.

Sources used in this calculation

Statutory figures such as tax and insurance rates come from the public bodies listed below. They change when the law is revised, so please also check the primary source before relying on the result for an important decision.

Statutory shares of inheritance and the share of a special beneficiary (Civil Code arts. 900, 903) — e-Gov Law Search (Digital Agency, Japan) Effective from 2019-07 ／ Last checked 2026-09-18

How we source and maintain these figures

How to use it

Enter the total value of the estate Use the whole estate, before any contribution is deducted.
Enter the composition of the heirs Choose the combination — spouse, children and so on — that fixes the statutory proportions.
Enter each heir's contribution The figure under discussion, or the figure you intend to argue for, can be entered as it stands.
Read the concrete shares The notional estate, net of contributions, is divided by the statutory shares and each contribution is then returned to the heir who made it.

Tips for getting more out of it

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 property held at the start of inheritance minus the value of bequests (Civil Code Art. 904-2(3)). This tool assumes there are no bequests and uses the total estate value as the cap, so if there are bequests the cap is lower by that amount. This tool shows a warning if the cap is exceeded, 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.

When this is useful

Preparing for a division meeting

Knowing what a successful claim would be worth focuses the discussion.

Proposing a figure for a contribution

Moving the amount shows the other heirs how their own shares respond.

Checking whether yours is a special contribution payment instead

If you are not an heir, the question is not the contribution share at all. This helps confirm the footing you are on.

Assembling material before conciliation

Fixing the numbers first makes it clearer which records are worth gathering.

Terms used here

Contribution share: The addition to an heir's statutory share where they made a special contribution to preserving or increasing the estate.
Special contribution: Contribution beyond what would ordinarily be expected. Cohabitation and everyday help are held not to reach it.
Notional estate: The estate less the contributions. Dividing this by the statutory shares is the backbone of the calculation.
Concrete share: What each heir finally takes: the statutory division of the notional estate, with the contribution returned to whoever made it.
Special contribution payment: Money a relative who is not an heir may claim from the heirs for care and similar service. Available since July 2019.
How the amount is fixed: By agreement among all the heirs first; failing that, by family court conciliation or adjudication.

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.

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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