The account that stops working when you land

An HSA is a US account paired with a high deductible health plan, holding money set aside for medical costs. Contributions are deductible, growth is untaxed, and withdrawals for qualifying medical care come out free of tax.

That triple benefit depends on US rules alone. Nothing in the arrangement obliges another country to recognize any of it.

Usually not, and the reason is the health plan rather than the move itself. Publication 969 makes eligibility turn on being covered by a high deductible health plan and holding no disqualifying other cover, so somebody relying on the NHS and a British employer's scheme generally falls outside it.

Residency is irrelevant to the test. A US citizen in Manchester who somehow kept qualifying US cover would still be eligible.

That rarely happens in practice. Most people who move take British cover and lose eligibility from the first month it starts.

So check the health plan before assuming contributions stopped. The date matters for working out whether anything went in while ineligible.

For 2026 the annual limits are $4,400 for self-only cover and $8,750 for family cover, with an extra $1,000 for anybody aged 55 or over at year end. The revenue procedure sets them.

The same document fixes what counts as a high deductible plan: a minimum deductible of $1,700 for self-only cover or $3,400 for family cover.

Out-of-pocket maximums cap the other end, at $8,500 and $17,000 respectively. A plan outside those boundaries is not a qualifying plan at all.

So the test is mechanical. Read the plan documents against the figures rather than relying on how the plan describes itself.

British tax law recognizes specific wrappers, and it recognizes them by name. An HSA appears on none of those lists.

The consequence follows from the general rule. Foreign income belongs on a UK resident's return, so interest and dividends arising inside the account are taxable here as they arise.

Realized gains work the same way. Selling a fund inside the HSA is a disposal for British purposes even though nothing taxable happened in American eyes.

So the HSA becomes an ordinary taxable brokerage account with extra paperwork. That is the single most important sentence in this article.

No, and the reason is definitional rather than political. The treaty's protection for cross-border savings runs through its pension article, and that article applies to a pension scheme as the treaty defines the term.

The definition requires an arrangement that is generally exempt from income tax in its home country and operated principally to provide pension or retirement benefits. A medical savings account fails the second limb.

Age 65 does soften the withdrawal rules, which tempts people to describe one as a retirement account. The treaty definition asks what the arrangement is principally for, not what it permits later.

So nobody should file a treaty position on this without advice. Our note on treaty disclosure explains what claiming one actually involves.

Three things, and the first is the obvious one. Any income arising inside the HSA is taxable in the UK, which eats into the compounding the account was built for.

The second is the mismatch in timing. US tax arrives on the way out, British tax arrives as income arises, so the two never line up neatly for credit purposes.

The third is the reporting. Somebody has to work out the UK income and gains inside an account the provider reports on no British statement.

So the carrying cost is real even in a year when nothing is withdrawn. Price it before deciding to leave the balance alone.

Take an American who moved to Bristol with an HSA invested in US index funds. She stops contributing, because her NHS cover ends her eligibility, and she leaves the money where it sits.

Each year the funds distribute dividends. Those are foreign dividends for British purposes, taxable as they arise, whether or not she takes a penny out.

When she rebalances inside the HSA, she realises gains that her US return ignores entirely and her British return does not. The paperwork lands on her alone.

In our practice this is the point where people ask whether holding cash inside it makes more sense. Often it does.

This part still works, and it is the strongest argument for keeping an HSA. A distribution that pays for qualifying medical care stays free of US tax wherever the care happens.

Publication 502 sets out what counts. Care received abroad is not excluded as such, though the rules on medicines are specific and catch people out.

A drug bought and used in another country can be included where it is legal in both that country and the United States. One brought into the United States generally cannot.

So private treatment in Britain can be funded from the HSA. Keep the invoices, because nobody files them but everybody needs them later.

It becomes taxable income, and before age 65 it also attracts an additional tax of 20% of the amount withdrawn. That is a serious rate, and it applies on top of the ordinary charge.

The additional tax falls away after age 65, on death, or where the account holder becomes disabled. Ordinary income tax still applies on the way out.

British tax then runs alongside it on whatever portion represents income arising while resident here. The interaction needs modeling rather than guessing.

So a withdrawal taken casually can cost far more than it looks. Work out the figure before moving the money.

Form 8889 goes in with the US return for any year of HSA activity, including a year where somebody else contributed. The form page sets out when it applies.

The trustee reports distributions separately, which means the Internal Revenue Service sees the withdrawal whether or not the form arrives. Mismatches generate letters.

An HSA is a US account, so it does not go on an FBAR. Our note on the reporting split explains which accounts land where.

So the US filing burden is modest. The British one, by contrast, is the part nobody prepares for.

Sometimes, and the window closes on the day residence starts. Qualifying medical expenses paid while still a US resident draw the balance down at no tax cost at all, which is the cleanest possible exit.

People moving with a large balance and known medical costs ahead should look at the timing seriously. A procedure brought forward by a month can be worth real money.

Emptying it for non-medical reasons is a different calculation entirely, because of the additional tax. Run both numbers.

So treat the balance as part of the departure checklist. Our note on leaving the US covers the direction of travel in reverse.

Simplicity wins once the shelter is gone. A balance generating little taxable income generates little British tax and little work.

Cash or a money market position produces interest, which is straightforward to report even though it is taxable. Funds that distribute and get rebalanced produce considerably more.

There is a separate trap for British residents holding non-US funds, which rarely bites inside an HSA because the holdings are American. Our note on identifying a PFIC covers that risk where it does arise.

So match the holdings to the reporting you are willing to do. The optimal portfolio changed the day you landed.

The first is contributing after eligibility ended. Excess contributions carry their own charge, and the longer they sit the more they cost.

The second is assuming an HSA is invisible to HMRC because no British statement arrives. The obligation sits on the taxpayer, not on the provider.

The third is treating the balance as a retirement pot. The rules that make it attractive at 65 are not the rules that make a pension work.

A fourth is forgetting the HSA entirely during a move, then discovering five years of unreported income at once.

An HSA belongs to the individual who opened it, so a non-American spouse does not become a US taxpayer by being married to the holder. That much is straightforward and frequently assumed to be otherwise.

Qualifying expenses can still cover a spouse and dependants, which is useful where family medical costs fall in Britain. The account holder claims them.

The British reporting position depends on who actually owns the account rather than who benefits. Joint arrangements complicate this considerably.

So keep the ownership clean. Our note on married filing separately covers the wider position.

We start by working out what is actually inside the HSA and what it produced in each year since the move. That evidence drives everything else.

Then we quantify the annual British cost of holding it, against the US benefit of keeping it for future medical spending. Those two numbers decide the question.

Where years have gone unreported, we look at the cleanest route to putting that right. Our US federal returns work covers the American side and we can talk through the British filings alongside it.

So the answer is specific to the balance and the holdings. There is no single right move here.