Your US will and your Japanese assets: the non-citizen spouse problem nobody explains

The short version. The “unlimited marital deduction” that lets a US citizen leave everything to a spouse with zero federal estate tax does not apply if your surviving spouse is not a US citizen (IRC §2056(d)). My wife is a Japanese citizen, so this is my problem too. The workarounds are a QDOT trust (which defers the tax, not erases it) plus annual gifting up to the non-citizen-spouse limit — $194,000 for 2026. On top of that, the US taxes the estate and Japan taxes each heir, so the same money gets measured from both ends. But the single highest-value thing you can do this week costs nothing: check the beneficiary designations on your 401(k), IRA and life insurance — they override your will entirely. I’m not a lawyer or a tax advisor; this is my own research, and cross-border estate planning needs a professional in both countries.

I’ll be honest about why I dug into this. I’m a Japanese national who spent four years working in the US, my spouse is Japanese, and most of our money is split across the two countries. Every “estate planning basics” article I read assumed both spouses were US citizens. That one assumption breaks the entire standard plan for families like mine — and probably yours.

The anchor: the marital deduction has a citizenship test

Here’s the rule almost nobody tells you. When a US citizen dies, they can normally leave an unlimited amount to their surviving spouse with no federal estate tax. That’s the unlimited marital deduction — the backbone of most US estate plans.

Under IRC §2056(d), that deduction is switched off if the surviving spouse is not a US citizen at the date of death. A green-card holder counts as a non-citizen here. So if you’re a US citizen married to a Japanese spouse who never naturalised, and you die first, your estate does not get the unlimited pass-through.

Instead, transfers to a non-citizen spouse are capped:

Mechanism	2026 figure	What it does
Annual gift exclusion to a non-citizen spouse	$194,000 (up from $190,000 in 2025)	Tax-free gifting per year to your non-citizen spouse
Regular annual gift exclusion (per other person)	separate, lower amount	Standard gifting to anyone else
Federal estate/gift lifetime exemption	~$15 million per person	Amount you can pass overall before federal estate tax kicks in

The lifetime exemption is large, so many families never hit federal estate tax at all. But if your combined US-side estate is substantial — a paid-off house, a heavy 401(k), a taxable brokerage that grew for 20 years — the citizenship gap is exactly where a plan that “looked fine” produces a surprise tax bill. These figures are indexed and change yearly; confirm the current numbers on IRS.gov before you act, not from a blog (including this one).

The main workaround: a QDOT (and one narrow escape hatch)

The structural fix is a Qualified Domestic Trust (QDOT) under IRC §2056A. Assets pass into the trust, the marital deduction is allowed, and the estate tax is deferred — not eliminated — until principal is distributed from the trust or the surviving spouse dies. Key mechanics:

• At least one trustee must be a US citizen individual or a domestic corporation. A US bank or trust company is only required as trustee (or as a co-trustee) when the QDOT’s assets exceed $2 million — or unless an alternative security arrangement is in place — that’s how the IRS keeps a hand on the deferred tax when the stakes are highest. (IRS Instructions for Form 706-QDT)
• The executor must make an irrevocable QDOT election on the estate tax return (Form 706). Miss it, and you can’t add it retroactively.
• Income distributions to the surviving spouse are generally not hit by the deferred tax; principal distributions are. The trust design matters.

The escape hatch: if the surviving spouse naturalises as a US citizen before the estate tax return is filed, the unlimited marital deduction applies and the QDOT becomes unnecessary. It’s a narrow window, but a real one worth knowing.

The two systems collide: US taxes the estate, Japan taxes the heir

This is the part that broke my brain. The two countries don’t just have different rates — they tax different people:

	United States	Japan
Who is taxed	The decedent’s estate (one taxpayer)	Each heir, on what they personally receive
Rate	Up to 40% federal above the exemption	Progressive 10%–55% per heir
Basic exemption	~$15M lifetime (per person)	¥30M + ¥6M per statutory heir (e.g. spouse + 2 kids = ¥48M)
Reach	Worldwide for US persons	Worldwide for heirs with sufficient Japan ties

The same transfer gets measured from opposite ends. A US–Japan estate tax treaty (in force since 1955, amended by a 2004 protocol) provides a credit mechanism so tax paid in one country reduces tax in the other — it softens double taxation but doesn’t erase it, and US state-level estate taxes aren’t covered.

The Japan side has a long arm: an heir (or decedent) with a Japanese address inside roughly the preceding 10 years can be taxed by Japan on worldwide assets inherited — not just Japan-situs property. That 10-year rule is why your US-only plan isn’t the whole picture, and it’s its own deep topic; confirm the current rule with a Japanese tax professional or the NTA rather than assuming.

Does your US will even govern your Japanese house?

Partly. Japan is a party to the 1961 Hague Convention on the form of wills, so a validly executed US will can be recognised in Japan. Recognition and usability are different things, though.

In practice, Japanese banks and the Legal Affairs Bureau (法務局, the land registry) run on Japanese-format paperwork. To act on a foreign will they typically want: the original will, a certified Japanese translation, apostille/authentication, and the family register (戸籍, koseki) proving heirship. That’s slow and expensive even when the will is legally valid.

Two more Japanese-law realities:

• Forced heirship — iryūbun (遺留分). Japan guarantees close heirs a minimum “reserved share.” A US will that tries to cut out a spouse or child can be partially unenforceable against Japan-situs assets.
• Many cross-border attorneys suggest a separate Japanese notarial will (公正証書遺言) for Japan-situs property, done before a Japanese notary with two witnesses — skipping the translation/authentication fight at the registry.

I’m not going to tell you a separate Japanese will is mandatory — it depends on what you own where. The action is to ask a professional whether one is warranted in your case.

The highest-value, lowest-effort move: check your beneficiaries this week

If you read nothing else, read this. 401(k)s, IRAs (traditional and Roth), and life insurance pass by beneficiary designation — outside your will entirely. Neither your US will nor a QDOT changes where they go. Whatever name is on that form wins.

People who moved abroad years ago often have a stale designation: an ex-spouse, a deceased parent, or a blank field left over from an employer plan at a job they had before the move. The cost of ignoring this isn’t hypothetical — a stale form can send a large IRA to the wrong person, and a non-citizen spouse can end up receiving it with full US income-tax liability and no QDOT structure to soften it. Hours to fix; potentially six figures to ignore.

So: log in to every US retirement account and life insurance policy and confirm the primary and contingent beneficiaries. If you already moved your accounts and updated addresses, see my notes on handling your 401(k) and IRA after moving to Japan — the same log-in-and-check habit applies here.

The quiet failure mode: heirs who can’t log in

Legal ownership means nothing if your heirs can’t reach the account. If your US 2FA codes go to a dead US phone number, or the account locks when it sees a Japanese IP, the money is functionally frozen — even though it’s legally theirs. I plan to carry my own US number to Japan for exactly this reason; the mechanics are in my write-up on keeping a US phone number for 2FA after you leave, and the recovery side is in getting locked out of your US bank from abroad. Accounts with no named beneficiary and no access plan don’t just get taxed — they get stuck in probate, which from Japan is slow and expensive.

Where to get real help

This is genuinely a two-professional problem: a US estate attorney (ideally one who has seen non-citizen spouses) and a Japanese one for the succession and inheritance-tax side. On the US filing and cross-border tax side, one place to start is Taxes for Expats, a US–Japan expat tax firm — it’s not the only option, just a starting point, and that link gives $25 off your first filing. (Full disclosure: that’s a referral link; I get a small credit if you file through it. Compare it against others and confirm everything against official IRS and NTA pages.)

FAQ

If my spouse becomes a US citizen, does all of this go away?

The estate-tax part largely does. If your surviving spouse is a US citizen — including naturalising before the estate tax return is filed — the unlimited marital deduction applies and a QDOT isn’t needed. It does not change Japan’s inheritance tax, which taxes the heir on worldwide assets when there are sufficient Japan ties.

Do I need both a US will and a Japanese will?

Possibly, but it’s case-by-case, not a rule. A US will can be recognised in Japan, yet Japanese banks and the land registry often demand translated, authenticated documents that make a separate Japanese notarial will faster in practice — especially if you own Japan-situs real estate. Ask an attorney in each country whether a second will is warranted for your specific assets.

What’s the one thing to do first?

Check your beneficiary designations on every US 401(k), IRA and life insurance policy. They override your will, they’re a common stale-data trap for people who moved years ago, and fixing them takes minutes. Do it before the attorney meeting — the conversation goes better when you already know what’s on those forms.