Investing as a Couple in Japan: Two NISAs, One Plan

Quick Answer: Japan has no joint investment accounts — every account belongs to one person. A couple therefore holds two NISAs (up to ¥3.6 million a year and ¥36 million lifetime combined) and plans across them. The traps are moving money between you (gift tax above ¥1.1 million a year) and accidentally breaking a dependent-spouse threshold with investment income.

Everything else on this site treats investing in Japan as an individual exercise, because Japanese law does. That's precisely the problem for couples: the accounts are individual, the tax thresholds are individual, and the pension categories are individual — but the money, the goal, and the retirement date are shared.

So the practical question isn't "which fund?" It's whose account, funded by whom, in what order — and that question has real tax consequences here that it doesn't have in countries with joint accounts and joint filing.

The good news is the arithmetic favours you. A couple in Japan can shelter twice what a single person can, and the structure that forces you to hold separate accounts also gives you two sets of allowances. You just have to use them deliberately.

This is educational information, not financial or tax advice. Thresholds, deductions, and pension rules change — confirm your own position with the NTA, your health-insurance provider, or a qualified professional before acting.

Why does Japan make couples invest separately?

Because there is no such thing as a joint securities account here.

Japanese brokers open accounts in the name of the person who will actually trade, and trading in someone else's name — 借名取引 — is prohibited. Major firms say so plainly in their own FAQs: SBI and Matsui both address the "can I trade in a family member's account?" question and the answer is no. You can sit together at the same laptop and agree on every decision, but the account, the tax reporting and the legal ownership belong to one of you.

Three consequences follow, and they shape everything below:

If you're setting up the accounts themselves, start with how to open a brokerage account in Japan as a foreigner — you'll each be doing it separately, and residence-card validity rules apply to each of you.

How much can a couple actually shelter?

This is the part worth internalising before the traps, because it's genuinely generous.

The FSA allows one NISA account per person, and the current limits are ¥1.2 million a year in the accumulation quota plus ¥2.4 million a year in the growth quota, inside an ¥18 million lifetime cap (of which at most ¥12 million can sit in the growth quota).

For a couple, that doubles:

One person A couple
Accumulation quota, per year ¥1.2m ¥2.4m
Growth quota, per year ¥2.4m ¥4.8m
Total per year ¥3.6m ¥7.2m
Lifetime tax-free cap ¥18m ¥36m

Two things about that table. First, almost nobody fills it — ¥7.2 million a year of surplus is far beyond most households, so in practice the couple's constraint is cash flow, not the cap. Work out what's actually investable from your combined take-home pay in how much of your Japan paycheck can go toward FI, or run both salaries through the Japan Salary Tax Calculator.

Second, the ¥36 million is only real if both accounts get used. A household that funnels everything into the higher earner's NISA has an ¥18 million ceiling and a spare account earning nothing. That's the single most common couple-level mistake in Japan, and fixing it runs straight into the next section.

Is it a gift if you fund your partner's NISA?

Yes — and this is where couples in Japan get caught, because in most people's mental model household money is simply household money.

Japan taxes gifts between spouses. Under 暦年課税 the basic exclusion is ¥1.1 million per recipient per calendar year, counting everything that person received from all donors combined; above that, gift tax applies and a return is due.

The obvious objection is that money between spouses is living expenses, and living expenses are exempt. That's true but much narrower than it sounds. The NTA's exemption covers amounts for living or education costs applied directly to those costs as needed — and it says explicitly that if the money is instead put into savings or used to buy securities or property, gift tax applies.

Read that against what you're trying to do. Transferring ¥2 million to your non-working partner so they can fill their NISA is, on the NTA's own description, money used to buy securities. It is not sheltered by the living-expenses exemption, and it's ¥900,000 over the annual exclusion.

What this means in practice:

The uncomfortable corollary: an account in your partner's name funded entirely by you may be treated as yours anyway when the tax office looks at whose money it really was. Deliberate, documented, within-the-exclusion transfers avoid that argument entirely.

Could investing income cost you the spouse deduction?

This is the trap that catches successful investors rather than careless ones.

If one of you is a dependent spouse for tax purposes, the household relies on the 配偶者控除, and the 2025 tax reform reset its thresholds. For 2025 onward, the spouse's 合計所得金額 must be ¥580,000 or less (up from ¥480,000) — which, with the ¥650,000 minimum salary deduction, means salary income up to ¥1.23 million. Above that, the 配偶者特別控除 tapers up to a spouse income of ¥1.33 million. Either way, the earning partner must have 合計所得金額 of ¥10 million or less to claim anything at all.

Now add investments, and note the mechanism carefully:

Gains inside a 特定口座（源泉徴収あり）don't count — unless you file. The NTA lists, among income excluded from 合計所得金額, gains on shares in a withholding-type 特定口座 where you have chosen not to file a return. The broker withholds 20.315% and the income stays invisible to the dependent-spouse test.

File a return on that same account and the income becomes visible. And filing is exactly what a sensible investor is tempted to do — to offset a loss at one broker against a gain at another, to carry a loss forward, or to reclaim tax. Do it for the dependent partner, and their 合計所得金額 can jump straight past ¥580,000, costing the household the spouse deduction, potentially in a year when the "gain" was a paper rebalancing rather than money you spent.

The point isn't that filing is wrong — sometimes it's clearly worth more than the deduction. The point is that for a dependent spouse in Japan it is a household decision with a number attached, not a routine tax optimisation. Work out both sides before filing.

And what about health insurance and the ¥1.3 million line?

A second, separate threshold, tested differently — and people routinely assume clearing one clears the other.

For social insurance, a dependent spouse (第3号被保険者) must generally have annual income under ¥1.3 million (¥1.8 million if 60 or over, or disabled) and, when living in the same household, less than half the insured person's income. Crossing it means paying pension and health premiums in their own right, which usually costs far more than the tax deduction ever did.

Two differences from the tax test matter here:

The pension side of dependency, including what those years actually build, is covered in dependent spouse pension in Japan.

Should a non-earning partner use iDeCo?

Usually not first — and the reason is specific to how the deduction works.

A Category III dependent spouse can join iDeCo, with a contribution cap of ¥23,000 a month. But iDeCo's headline benefit is that contributions are deducted from taxable income, and a deduction is worth nothing against income you don't have.

Here's the detail that surprises couples: you can't move the deduction to the working partner. The NTA's social-insurance deduction is explicitly written to cover premiums a taxpayer pays "for themselves or for a spouse or other relative sharing their household" — which is why paying your partner's National Pension premiums does reduce your tax. The deduction that covers iDeCo (小規模企業共済等掛金控除) carries no such extension; it describes contributions the taxpayer paid, full stop.

So funding your non-earning partner's iDeCo produces a deduction for nobody, while locking the money until they turn 60 — with fees running the whole time and no early exit unless narrow conditions are met. For a household in that position, the lower earner's NISA does the same tax-free-growth job with none of the lock.

That calculus changes the moment the dependent partner earns enough to pay income tax, or if the 2027 changes alter your category's cap — see iDeCo 2026–2027 changes for foreigners and, if you're deciding between the two accounts at all, iDeCo for beginners in your first years in Japan.

Whose account should hold what?

There's no universal answer, but there are four questions that usually settle it — and none of them is "who's better at investing."

1. Who has the income? Each partner investing their own earnings is the structurally simplest arrangement and sidesteps gift tax entirely. Start there and only deviate for a reason.

2. Is one of you more likely to leave Japan? Residency decides what survives. A 特定口座 is deemed closed when its holder stops being a resident, a NISA usually closes with it, and iDeCo generally locks until 60 — but only for the partner who leaves. In an international couple where one partner holds Japanese nationality and the other doesn't, the exposure is genuinely asymmetric: a Japanese national abroad can enrol voluntarily in the National Pension and keep contributing to iDeCo; a foreign national abroad cannot. The full picture is in investing when you leave Japan.

3. Does one of you sit near a threshold? If one partner is a dependent spouse, holdings likely to generate large realised gains sit more comfortably in the other partner's account, where a filing decision doesn't jeopardise a deduction.

4. What happens if one of you dies? Japan's inheritance tax gives a surviving spouse a substantial credit — inheritance tax is effectively eliminated on the greater of ¥160 million or the spouse's statutory share — but it requires the estate to be divided by the filing deadline (or a formal extension notice within three years). Cross-border couples have the additional problem that assets, wills, and tax residency may span two countries. Concentrating everything in one name makes that harder, not easier.

None of this argues for a rigid 50/50 split. It argues for knowing why the balance is where it is.

How do you actually decide this together?

The mechanics above are the easy half. The half that decides whether the plan survives is agreeing on the target, the timing, and the tolerance — how much you're aiming for, when each of you stops working, and how much volatility you can both live with.

That's where separate accounts stop being a legal technicality and start being a planning problem. Two accounts, two retirement dates, possibly two countries and two currencies — but one shared number. Model it as one household in the PlanTogetherFI calculator, then use the couples guides to pressure-test the assumptions:

And for the underlying investing decisions you'll each make inside your own account, what to invest in: how to choose a fund in Japan and the overview at how to invest in Japan as a foreigner.

Frequently Asked Questions

Can a married couple open a joint investment account in Japan?

No. Japanese brokers open accounts in the name of the individual who will trade, and trading in another person's name (借名取引) is prohibited — SBI and Matsui both state this in their published FAQs. Couples invest through two individual accounts and coordinate outside them.

How much can a couple invest in NISA per year?

Twice the individual limits, because each person has their own account: up to ¥2.4 million a year combined in the accumulation quota plus ¥4.8 million in the growth quota — ¥7.2 million a year — within a combined lifetime cap of ¥36 million. Most households are limited by cash flow long before any of that.

Can I put money into my spouse's NISA?

You can transfer money to them, but it's a gift for tax purposes. The annual exclusion is ¥1.1 million per recipient, and the living-expenses exemption doesn't help: the NTA states that money saved or used to buy securities is taxable rather than exempt. Staying inside the annual exclusion, or having each partner invest their own income, avoids the issue.

Does investment income affect the spouse deduction?

It can. Gains in a 特定口座 with withholding are excluded from the 合計所得金額 test only if you choose not to file a return on them. File — to offset losses across brokers, for instance — and the income counts, which can push a dependent spouse past the ¥580,000 limit and cost the household the deduction.

Is the tax threshold the same as the ¥1.3 million dependency threshold?

No, and this catches people. The tax deduction turns on the spouse's 合計所得金額 (¥580,000, tapering via the special deduction to ¥1.33 million). Social-insurance dependency is a separate test — generally under ¥1.3 million a year and less than half the insured partner's income — using a broader definition of income. You can clear one and fail the other.

Should my non-working spouse open an iDeCo?

Rarely as a first step. The contribution cap is ¥23,000 a month, but the tax deduction is worthless without taxable income, and it cannot be claimed by the earning partner — unlike National Pension premiums, which a spouse can pay and deduct. Meanwhile the money locks until 60. A NISA gives the same tax-free growth with no lock.

Who should hold the investments if one of us might leave Japan?

Weigh it deliberately, because residency — not the marriage — decides what survives. The departing partner's 特定口座 is deemed closed, their NISA usually closes with it, and their iDeCo generally locks until 60, while the remaining partner's accounts are unaffected. See investing when you leave Japan.

PlanTogetherFI is for educational planning only. It is not financial or tax advice, and we don't recommend specific brokers or products. Tax thresholds, dependency rules, and contribution limits change, and gift, inheritance, and cross-border questions are fact-specific — confirm your own position with the NTA, your health-insurance provider, and a qualified professional before acting.

Sources and further reading

Thresholds, limits, and certification practice reflect published rules as of August 2026 and change — confirm with the NTA, your insurer, and your provider before acting.