Japan's Statutory Inheritance Calculator | A Reference for Cross-Border Heirs

If you are a non-resident heir of a Japan-based estate, an executor working on Japanese assets from abroad, or an estate planner advising a client with property in Japan, you will eventually need the baseline ratios that Japanese family courts and probate practitioners actually use. This tool reproduces them: statutory share (法定相続分, Article 900 of Japan's Civil Code) and reserved portion (遺留分, Article 1042).

Scope: this calculator implements Japanese inheritance law only. US state intestate succession (with its split between community-property and common-law states), the UK Inheritance (Provision for Family and Dependants) Act, Australian state acts, and other Anglosphere systems differ in structure and are not modeled here.

💡 About this tool

Inheritance handled under Japanese law looks unusual to a reader trained on Anglosphere succession.

• The spouse is always an heir, but never sole. Unlike a US "elective share" or UK family-provision claim, the surviving spouse in Japan automatically inherits alongside whoever sits in the top surviving priority tier. The spouse's share scales: 1/2 with children, 2/3 with the deceased's parents, 3/4 with the deceased's siblings.
• Three rigid priority tiers. Children come first. Only if no children (or grandchildren by representation) survive do the deceased's parents inherit. Only if neither children nor parents survive do siblings inherit. There is no concept of "all descendants share equally with the spouse" as in some common-law states.
• Reserved portions (legitime) but for the right people. The reserved portion that protects against disinheritance only applies to spouses, children, and lineal ascendants. Siblings get zero protection — a will can completely cut them out.
• Children inherit equally, regardless of birth order or marital status. A 2013 Constitutional Court ruling made children born out of wedlock equal to marital children, putting Japan in line with most OECD jurisdictions.

🧐 Frequently Asked Questions

Q. I'm a US heir of a Japanese decedent. Does Japanese law apply to me?

A. It depends on where the assets are and what the decedent's nationality was. Japanese-situs real estate is governed by Japanese inheritance law regardless of heir residence. Movable assets and cross-border issues are decided under Japan's Act on General Rules for Application of Laws (法の適用に関する通則法), which generally applies the decedent's national law — so a Japanese citizen's worldwide estate often falls under Japanese law even if heirs live abroad. Consult a Japanese lawyer (弁護士) qualified for international estates.

Q. Why do siblings show "None" for the reserved portion?

A. Article 1042 of Japan's Civil Code excludes siblings from the legitime entirely. The deceased may write a will leaving everything to charity or a spouse and the siblings have no legal claim to claw any portion back. This is harsher than most Western systems where siblings sometimes have a family-provision claim.

Q. Can a non-resident heir refuse inheritance in Japan?

A. Yes — heirs can renounce inheritance (相続放棄) by filing with the family court within three months of learning of the death. This is commonly done when the estate is more liabilities than assets, or when one heir wants to consolidate the estate in another heir's hands.

Q. Is the result of this calculator binding in a Japanese court?

A. No. It is a baseline reference. Real Japanese estates are also shaped by wills (遺言), special contribution claims (寄与分), advance gifts to heirs (特別受益), renunciation, and representation by grandchildren or nieces/nephews. A Japanese family court mediator or judge will apply these adjustments.

📚 Japan vs. the Anglosphere — how the systems diverge

A few comparisons that often surprise heirs encountering Japanese inheritance for the first time:

Versus US community-property states (CA, TX, AZ, etc.): Japan has no concept of marital community property at death. The spouse inherits a defined fraction of the entire estate as an heir, not "half by default plus a share of the rest." Practitioners drafting cross-border estate plans often need to disentangle US community property classification before applying the Japanese fractions.

Versus US common-law states (NY, NJ, MA, etc.): Most US states give the surviving spouse a larger share when children are common, and a smaller share when stepchildren are involved. Japan applies the flat 1/2 regardless. This produces dramatically different outcomes for blended families.

Versus UK and Australia: Both jurisdictions allow flexible family-provision claims where dependents can ask the court to override an unfair will. Japan's legitime is mathematical and non-discretionary — siblings (third tier) simply have no claim, period.

Versus civil-law neighbors (Korea, Taiwan): Korea has a near-identical structure (a legacy of shared 20th-century legal reform), while Taiwan applies different fractions for the spouse-with-children case (1/n+1 each, rather than 1/2 to spouse). Quick sanity check before applying Japanese fractions to Korean or Taiwanese assets.

For an active case, the recommended professional is a Japanese 弁護士 (bengoshi, qualified attorney) with international-estate experience, supplemented by a 司法書士 (shihō-shoshi, judicial scrivener) for the land-registry steps. Tax obligations are separately handled by a 税理士 (zeirishi, tax accountant) — inheritance tax in Japan is among the world's heaviest at the top brackets (up to 55%).