You opened a savings account for your daughter. America opened a file on her

Figures relate to tax year 2025-26 (UK) · 2025 (US)

Your daughter was born in London and holds an American passport because you do. You opened a savings account for her, paid in a little each month, and never thought about it again.

America thinks about it. A Junior ISA is tax free in Britain and completely invisible to HMRC, but your daughter is a US taxpayer from birth. The wrapper means nothing across the Atlantic.

Key takeaways

• An American child is a US taxpayer from birth, whatever their age.
• A Junior ISA is tax free in Britain only, never in America.
• A stocks and shares version holding UK funds can trigger punitive fund rules.
• A cash version is far simpler, producing ordinary interest income.
• Foreign account reporting can apply to a child once balances build up.
• Unearned income above a small threshold can be taxed at the parents' rate.

What is a Junior ISA?

It is a British savings or investment account for a child under eighteen, with an annual subscription limit and no British tax on the income or growth. The money belongs to the child and they cannot touch it until they turn eighteen. According to HMRC guidance, it comes in a cash version and a stocks and shares version.

Child Trust Funds work on a similar principle to a Junior ISA for an older group of children.

Both are genuinely good products in Britain. The problem starts one border away.

Why does America care about a child's account?

Because citizenship rather than age decides who files. A child born abroad to an American parent is usually a US citizen from birth, and citizens are taxed on worldwide income at any age. There is no minimum age and no exemption for pocket money accounts.

So the account belongs to a small taxpayer with filing obligations of their own.

Parents sign on the child's behalf. The obligation still sits with the child.

Which version causes the trouble?

The stocks and shares Junior ISA, and specifically what sits inside it. British funds and investment trusts are foreign funds to America, and they fall under a punitive regime with annual reporting and high rates. A cash account produces plain interest and causes very little difficulty by comparison.

That single choice changes the entire American position.

Our guide to the ISA and PFIC problem explains the regime in detail for adults.

A worked example

The figures below are illustrative and use round numbers to show the mechanics.

Emma, aged nine, holds a stocks and shares Junior ISA worth £18,000 invested in two British index funds. Her parents pay in £200 a month.

Britain taxes none of it. America sees two foreign funds, each needing an annual form, with tax and an interest charge falling due when they are eventually sold.

Switching her to a cash Junior ISA would leave one simple interest figure a year. The difference in professional fees alone runs to hundreds of pounds annually.

Does the child have to file a US return?

Sometimes, and it depends on the income rather than the balance. A child with unearned income above a modest threshold has to file, and interest and dividends both count. Many children with small accounts fall below it and file nothing at all.

Fund holdings can create a filing requirement even without a sale.

Check the position each year. Thresholds move and balances grow.

What is the kiddie tax?

It stops families sheltering investment income in a child's name. Above a set amount, a child's unearned income is taxed at the parents' marginal rate rather than the child's own low rate. The threshold is small, so a growing account reaches it faster than people expect.

It applies to the income, not to gifts you make into the account.

So the planning value of saving in a child's name is smaller in the American system than in the British one.

The two versions compared

Does foreign account reporting apply?

It can. A child with foreign accounts whose combined balances pass the reporting threshold at any point in the year has a filing obligation, and a parent signs on their behalf. The threshold looks at all their accounts together rather than each one separately.

Separate asset reporting has much higher thresholds for a child living abroad.

Our guide to FBAR deadlines and penalties covers how the reporting works.

What about a Child Trust Fund?

The same logic applies, and many of these have now matured into adult accounts. A young adult who has just gained access may hold British funds without realising America treats them harshly. Reviewing it at eighteen is far better than discovering it at thirty.

Some have sat unclaimed for years because nobody told the child they existed.

Providers hold unclaimed accounts indefinitely. A short online search using the child details usually locates one.

Trace it first, then look at what it holds. The order matters.

Is it treated as a foreign trust?

Generally no, and that is a relief. Most advisers treat these accounts as custodial arrangements for a child rather than trusts, which keeps the heaviest trust reporting away. Views are not entirely uniform, so the position deserves a look rather than an assumption.

Trust treatment would add substantially more paperwork.

Our guide to UK trust distributions and US tax covers genuine trust arrangements.

What if grandparents pay in?

Ordinary contributions at this level rarely cause a problem. Large gifts from a person who is not American can trigger a reporting form for the recipient, but the threshold sits far above an annual subscription limit for a child's account.

Keep a note of who paid in and when.

That record matters more if a much larger gift follows later.

What counts as a fund for these rules?

Almost any pooled British investment. Unit trusts, open-ended investment companies, investment trusts and most exchange traded funds listed here all qualify. The test looks at the company behind the holding rather than the label on the factsheet.

Shares in a single trading company do not count.

Nor does cash on deposit. That is why the cash version stays simple.

Do both parents need to be American?

No, one is usually enough. Citizenship passes to a child born abroad where an American parent meets certain residence conditions before the birth, so a single American parent can make the child a taxpayer.

Many parents are unsure whether their child qualifies. It is worth confirming rather than guessing.

If the child has an American passport, the question is already answered.

Can you just close the account?

Not easily, because the money belongs to the child and stays locked until eighteen. You can usually stop paying in and switch what the account holds, which solves most of the problem without touching the balance.

Transferring between providers is allowed and does not break the wrapper.

So the realistic choice is what it invests in, not whether it exists.

How to review the account

1. Confirm whether your child is a US citizen, which usually follows from your own status.
2. Establish whether the account is the cash version or the investment version.
3. List every fund inside it, with the provider and the holding value.
4. Work out the child's total unearned income for the year in dollars.
5. Add up all their foreign accounts to test the reporting threshold.
6. Decide whether to switch the holdings before the balance grows further.
7. Diarise a review at each birthday, and definitely before they turn eighteen.

Should you switch to cash?

Often yes, at least while the child is American and the Junior ISA is modest. A cash account gives up some expected growth and removes a reporting regime that can cost more in fees than the investment earns. That trade favours cash for most families we meet.

Larger balances deserve a proper calculation rather than a rule of thumb.

Check any exit costs with the provider first. Most charge nothing to switch funds inside the wrapper.

Individual shares are a third route, since a single company holding is not a fund.

What happens when they turn eighteen?

A Junior ISA becomes theirs and converts to an adult account, which changes nothing in America. A young adult who starts work also starts filing on their own account, and an inherited fund problem can land on them at the worst possible moment.

Eighteen is the natural point to clean it up.

Explain the position to them as well. They will be the one filing.

Does it affect university or first jobs?

Only through the return. A student with a British account and an American passport keeps filing, and the account appears on that return like any other. It does not affect British student finance, which looks at household income rather than citizenship.

Our guide to study abroad tax rules covers the student position.

Get them into the habit early. A first return at eighteen is easier than a catch-up at twenty-five.

What does the paperwork cost each year?

Very little for a cash account, because there is usually nothing extra to prepare. An investment account holding several British funds is a different matter, since each holding can need its own annual form and the working behind it takes real time.

Families regularly pay more in fees than the account earns.

That imbalance is the strongest argument for keeping it simple while the child is young.

Does the child need a US tax number?

Yes, before any return can be filed. An American child born abroad needs a social security number, and the application goes through the embassy alongside the passport and citizenship paperwork.

Apply early. The process takes months rather than weeks.

Without the number, even a simple return cannot go in on time.

Mistakes and penalties we see with a Junior ISA

The first is assuming a child holding a Junior ISA is too young to matter. Citizenship starts at birth and so does the obligation.

The second is choosing funds because the British tax treatment is excellent. It is, and the American treatment is the opposite.

The third is missing the account on foreign account reporting once balances build.

The fourth is leaving it until the child is an adult with a problem they did not create.

How US UK Tax Accountants helps

We look at what the account actually holds, work out whether your child needs to file at all, and tell you whether switching is worth doing at the current balance. Then we prepare whatever returns are genuinely required.

We also review accounts reaching maturity before they become an adult problem. Our US federal return service covers the filing.

If your child holds a British savings account and an American passport, get in touch. Fixing this at nine costs very little. Fixing it at nineteen does not.

Last reviewed 28 September 2026. This article is general information and not personal tax advice. Every family turns on its own facts, so take advice on yours before acting.