By Dako & Jay
In our house we talk about “our retirement money” the way most couples do. One number, one plan, one future. The IRS has never once seen it that way.
A 401(k) is an individual account. Not household, not joint, not “ours.” Each one belongs to exactly one name. So when a mixed-nationality couple starts asking what happens to my 401(k) if my Japanese spouse wants to move home, the honest answer begins with a split: her account and your account are about to have two different stories, because she and you carry two different passports.
I’m Dako, the Japanese half of this marriage, and I hold a green card. Jay, my American husband, will jump in below. We each have our own 401(k) from our own jobs, we’re planning for FIRE, and we still haven’t decided whether we’re staying in the US, moving to Japan, or splitting time between both. This post is the research I wish I’d had when we first started weighing a move ourselves.
The scenario: one spouse leaves, one spouse stays (or you both go)
Picture the version of this that search engines see all day. An American married to a Japanese citizen. Two careers, two 401(k)s, kids with two passports. One day the Japanese spouse says the thing that’s been building for years: I want to go home. Maybe it’s aging parents. Maybe it’s just the pull of the place.
Whatever the reason, the retirement accounts suddenly matter in a way they didn’t last week. And the first instinct many couples have, “we’d better cash out before we leave,” is the single most expensive idea in this whole topic.
So let’s slow it down and take the accounts one at a time, because that’s how the tax code takes them.
What happens to the US-citizen spouse’s 401(k)
Short version: almost nothing, no matter where you live.
A US citizen is taxed by the US on worldwide income for life. Move to Tokyo, and Jay’s 401(k) stays parked at the same provider, growing the same way, taxed by the same country under mostly the same rules as if he’d never left. Japan will have opinions about his distributions once he’s a Japanese tax resident, and coordinating the two systems is real work. But there’s no event where his account gets frozen, seized, or forcibly cashed out just because he changed address.
The practical friction is smaller and dumber. Some plan providers and brokerages restrict what customers with foreign addresses can do. Policies differ by company and change over time, so this is a phone call to make before the movers come, not after.
Jay here. The phrase that rewired my brain was “individual account.” I’d mentally filed both 401(k)s under one label: ours. Dako’s research made me realize the government files them under two labels with two completely different rulebooks attached. Nothing about being married merges them. The one place marriage does show up: if I wanted to name anyone other than Dako as my death beneficiary, most plans would require her written, witnessed consent. The rulebook cares about my marriage exactly once, and it’s there.
Your options when someone actually leaves: leave it, roll it, or cash it
For whichever spouse stops working in the US, the menu has three items.
- Leave the 401(k) where it is. Balances over $7,000 can’t be forced out of the plan without your consent. The money keeps compounding under US rules until you draw it in retirement.
- Roll it over to an IRA. Same tax-deferred status, usually more investment choice and lower fees. The catch for movers: IRA custodians have their own foreign-address policies, so open and fund it while you still have a US address.
- Cash out. The balance becomes ordinary income immediately, plus a 10% penalty if you’re under 59½ (with limited exceptions, like separating from service at 55 or later). For a couple in their peak earning years, this can vaporize a third of the account or more.
Rushing toward option three out of fear is exactly the mistake this post exists to prevent. The account survives your move. Fear of losing it is not a reason to actually lose a third of it.
One small-print exception to “nothing happens”: if a leftover 401(k) holds under $1,000, the plan can simply mail a check, and between $1,000 and $7,000 it can sweep the money into an IRA on its own. Worth knowing if either of you has a small orphan account from an old job.
The non-citizen spouse’s account is where it gets interesting
My 401(k) is the complicated one, because my relationship with the US tax system is the thing that changes.
As long as I keep my green card, even living in Japan, I remain a US tax resident. My distributions get the same US treatment as his. I keep filing US returns from Japan. Keeping the card, though, has its own running costs and its own clock, which I’ll come back to.
If I instead give up the green card and become a plain nonresident alien, the default rule says US pension payments to me get hit with 30% withholding. The US-Japan tax treaty softens this dramatically: pensions paid to a resident of Japan are, under the treaty’s pension article, taxable only in Japan. Claiming that treatment takes paperwork, a Form W-8BEN to the plan, possibly a 1040-NR to recover excess withholding, and the treaty position around lump-sum withdrawals has genuine wrinkles. Meanwhile Japan, as my new home, would tax those distributions under its own categories, and how Japanese law classifies a 401(k) withdrawal is a question big enough that we’re saving it for a post of its own.
And the 10% early-withdrawal penalty? It doesn’t care about any of this. Take the money before 59½ and the penalty logic still applies, resident or not.
Then there’s the trap door under the whole floor: timing. Hold a green card in 8 of the last 15 tax years and give it up, and I’d exit as a “long-term resident” under the expatriation rules. That’s the same regime we covered in our post on covered expatriate status. Fail one of those wealth or compliance tests and my 401(k) gets the harshest label in this article: for a covered expatriate, future 401(k) distributions carry a permanent 30% withholding, with treaty relief signed away. A FIRE-sized portfolio makes that scenario less hypothetical than it sounds.
Planning ahead as a couple: how we approach it
Here’s what all of the above turned into at our house, and it’s almost embarrassingly simple: both 401(k)s stay untouched until retirement, in every scenario we’re considering.
Full move to Japan, half-and-half life, staying put in the US: in each version of the plan, the accounts remain American, invested, and undisturbed. We treat them as the one part of the balance sheet that doesn’t get to react to homesickness. What we spend our planning energy on instead is sequencing: whose card, whose years, whose distributions land in which country, and when. The 8-of-15 clock on my green card is a bigger input to our timeline than either account balance.
Jay here, one more time. What I’d tell the American spouse reading this: when “I want to go home” arrives at your dinner table, the retirement accounts feel like the fragile thing, and they’re actually the sturdy thing. They can wait decades. The decisions that can’t wait are the status ones, her green card, the years already on its clock. Protect the accounts by ignoring them, and spend your worry on the calendar.
We’re not advertising our approach as the right one. A couple who knows they’re leaving in eighteen months might reasonably roll everything to an IRA now. A couple who’ll never leave has no reason to read this far. Ours is the plan of a family that refuses to decide, and it’s built so that refusing stays affordable.
FAQ
Do I lose my 401(k) if we move to Japan?
No. The account stays open and invested regardless of where you live or what passport you hold. Provider service restrictions for foreign addresses are the practical annoyance to check, not confiscation.
Should the Japanese spouse cash out before moving home?
Almost never as a first instinct. Cashing out means immediate ordinary income tax plus, before 59½, usually a 10% penalty. Compare that against leaving the account alone, or a treaty-based claim on distributions taken later from Japan, before touching anything.
What happens if the US-citizen spouse dies first, abroad, with a non-citizen widow?
The beneficiary designation still controls who gets the money. But estates with a non-citizen surviving spouse lose the unlimited marital deduction, the automatic rule that lets assets pass between spouses untaxed, unless specific structures like a QDOT are in place. With the 2026 federal exemption at $15 million per person, most families never hit the tax itself. The planning rules are strange enough around non-citizen spouses that this is a named topic to raise with an estate attorney, not something to improvise.
Can we combine our 401(k)s since we’re married?
No. There is no mechanism for merging retirement accounts between living spouses, regardless of citizenship. Each account rides on its owner’s status. That’s the entire premise of this post, and the reason a mixed-nationality couple needs a per-person plan.
If you do one thing after reading, make it a two-column list: every retirement account in the household, whose name is on it, and that person’s citizenship or immigration status next to it. Every question that matters starts from that table.
This article is general information about US tax rules, not tax or legal advice. Cross-border retirement planning depends heavily on your specific status, treaty positions, and timing. Please talk to a qualified cross-border tax professional before acting, and see our Disclaimer for details.