Japan's Forced Heirship System (Iryubun)

Even with a valid will, Japanese law guarantees certain family members a minimum share of the estate that cannot be overridden. This system is called iryubun — and it's one of the biggest surprises for English speakers accustomed to the testamentary freedom of common law countries.

In the US, UK, or Australia, you can generally leave your entire estate to anyone you choose. In Japan, you can't.

Who Gets a Reserved Share

The iryubun system protects three categories of heirs:

• Surviving spouse — always protected
• Children (including adopted children) — always protected
• Direct ascendants (parents, grandparents) — protected only when there are no children

Siblings of the deceased are explicitly excluded from iryubun. A will can completely disinherit siblings with no legal recourse.

How Much Is Reserved

The reserved portion depends on who the surviving heirs are:

When children exist (with or without a spouse): The total reserved portion is 1/2 of the entire estate. Each protected heir's individual iryubun is calculated as their statutory share multiplied by 1/2.

Example: Deceased leaves a spouse and two children. The spouse's statutory share is 1/2, so their iryubun is 1/4 of the total estate. Each child's statutory share is 1/4 (half of the children's collective 1/2), so each child's iryubun is 1/8.

When only parents survive (no children): The total reserved portion drops to 1/3 of the estate. The parents' individual iryubun is their statutory share multiplied by 1/3.

What Happens When a Will Violates Iryubun

If a will leaves less than the iryubun to a protected heir, the will is not automatically invalidated. The shortchanged heir must actively file an iryubun infringement claim (iryubun shinko seikyu) to recover their minimum share.

The claim has a one-year statute of limitations from when the heir learns of the death and that their iryubun was infringed. There's also an absolute ten-year cap from the date of death.

This means a protected heir can choose not to exercise their iryubun rights — perhaps because they want to honor the deceased's wishes. But if they do claim it, the other beneficiaries must compensate them, typically through cash payment rather than redistributing specific assets.

Can You Disinherit Someone Entirely?

Complete disinheritance (haijo) of an iryubun-protected heir requires a formal petition to the Family Court. Courts grant this only in extreme cases — severe criminal conduct or documented abuse directed at the deceased. Simply being estranged or on bad terms is not sufficient.

Why This Matters for Foreign Families

For expats in Japan, iryubun creates two practical problems:

First, if you've written a will in your home country that leaves everything to a specific person (a new spouse, a charity, a business partner), Japanese iryubun may override that will's effect on assets located in Japan. Your Tokyo apartment or Japanese bank accounts may be subject to forced division regardless of what your will says.

Second, the intersection of iryubun with the renvoi doctrine means which country's law applies can depend on the type of asset. Your US will might govern your American bank accounts, but Japanese law (including iryubun) governs your Japanese real estate.

The Japan Death Guide for English Speakers includes flowcharts mapping statutory shares, iryubun calculations, and the claim process.

See more Japan guides →