Moving to Britain for the last chapter, and what it costs

Your tax residence, which is a statutory test rather than a feeling. The statutory residence test counts days, ties and past presence, and it decides when British tax starts reaching your worldwide income.

A visa is immigration. Residence is tax. The two can disagree.

HMRC publishes the statutory residence test guidance in full.

No, and that is the fact everything else builds on. American citizens and Green Card holders file on worldwide income wherever they live, so retiring to the UK adds a tax system rather than swapping one.

Two returns become the normal state of affairs.

Relief then comes through the treaty and through credits, not through absence.

Britain alone, once you live here. The treaty says payments made by one country under its social security legislation to a resident of the other are taxable only in that other country. An American benefit paid to a British resident therefore belongs to Britain.

Crucially, that paragraph survives the saving clause.

So this is one of the rare cases where an American citizen genuinely escapes American tax on American-source income.

Harder, because the treaty splits them in two. Regular income from a pension scheme goes to the country where you live, and a lump sum goes to the country where the scheme sits. Neither of those paragraphs survives the saving clause for citizens.

So both countries reach a typical withdrawal, and credits relieve the overlap.

A qualified Roth distribution is the exception worth knowing, since the paragraph covering it does survive.

The IRS page for the UK treaty documents links the convention and the protocol that amended it.

There is, and it is generous for the right person. A four-year regime for foreign income and gains applies from 6 April 2025, open to someone in their first four years of British residence after at least ten consecutive years of non-residence.

It replaced the old remittance basis rather than sitting alongside it.

The GOV.UK guidance on the four-year regime sets out the conditions.

It does not, and the boundaries matter. The guidance describes it as covering foreign income and gains such as overseas trade profits, foreign property profits, non-UK dividends and foreign bank interest, while foreign employment earnings sit outside it.

Whether a particular source qualifies is a question to settle before you arrive.

So take advice on your own income list rather than assuming the label covers all of it.

They meet two sets of rules that disagree about what a fund is. American mutual funds and exchange traded funds are ordinary holdings at home, and Britain may treat them as non-reporting offshore funds, taxing gains as income.

British funds carry the mirror problem under American rules.

So review the portfolio before the move, while selling is still a choice rather than a consequence.

Retirement accounts are the exception worth noting. A 401(k) or an IRA is a pension scheme rather than a fund holding, so it follows the treaty rather than the offshore fund rules.

Once you have been here long enough, under a test that changed recently. Since 6 April 2025 inheritance tax follows long-term residence rather than domicile, reaching someone resident for the previous ten consecutive years or for ten years within the previous twenty.

That brings worldwide assets into charge, not just British ones.

HMRC sets it out in its guidance for long-term UK residents.

Not immediately, because the status has a tail. Someone who leaves stays within scope for a period that depends on how long they were resident, running up to ten tax years and reducing for shorter histories.

A ten to thirteen year stay carries a shorter tail than a twenty-year one.

So retiring to the UK is a decision with a long horizon on the estate side.

Anyone retiring to the UK with a possible return in mind should model that tail at the outset. It is far easier to plan for than to escape.

They do, and not always kindly. American estate tax follows citizenship, so an American can face both systems on the same assets, with relief depending on the estate and gift provisions rather than the income treaty alone.

Spouses who are not American complicate it further.

We cover the ground in inheritance tax when one of you is American.

It stays American for most purposes, and Britain starts taking an interest in what it earns. Rent becomes taxable here once you are resident, with credit for the American tax on the same income, and a later sale raises a second set of questions.

The main residence relief you expected may no longer apply once you have moved out.

So decide early whether the house is a home you will return to or an investment you happen to own.

It is not a tax, and it belongs on the same spreadsheet. Visa routes often carry an immigration health surcharge payable upfront, and the amount depends on the length of the visa granted.

That is an immigration cost rather than a tax one, and it lands in the same year as the move.

Budget for it alongside the removal van, not alongside the tax return.

Check the current amount at the point of application. It has risen more than once and it is charged for the full visa length upfront.

Sometimes, and it depends entirely on which state you left. A few states take a narrow view of when residence ends and keep asserting a claim long after the federal position is settled, particularly where you kept a home or a driving licence there.

Leaving the country does not automatically end a state filing obligation.

So cut the ties deliberately and keep the evidence, rather than assuming distance does it for you.

Close accounts, surrender licences and register to vote where you now live. Evidence of intent is what settles these arguments.

Enormously, because the two tax years do not align. Britain runs to 5 April and America to 31 December, so arriving in February produces a short British year and a full American one, with income split awkwardly between them.

Split-year treatment can help where the conditions are met.

Arriving early in a British tax year is usually simpler than arriving late in one.

Retiring to the UK in April rather than February can simplify two years of filings at once. It is the cheapest planning decision on this whole list.

They change the estate planning far more than the income planning. Transfers between spouses are usually unlimited in Britain, and American rules restrict them where the recipient spouse is not American, which cuts across the obvious arrangement.

Filing status on the American return is a separate decision again.

So plan the two estates together rather than assuming a mirror will do.

Work through these in order, ideally in the tax year before you arrive. Several of them cannot be done afterwards.

Register, decide and document, in that order. You may need to register for Self Assessment, decide whether to claim the new-arrival relief, and write down the residence position that every later year depends on. None of those three is difficult on its own, and all three are awkward to reconstruct two years later.

Currency conventions set in year one should carry through every later year.

Our clients who treated the first year as setup rather than as a filing found every subsequent year straightforward.

Take an American couple moving to Somerset after forty years in Boston. Their social security becomes taxable only in Britain, which surprises them pleasantly.

Their traditional pension withdrawals reach both systems, with credits relieving the overlap, while a Roth balance behaves differently again.

Having been non-resident for decades, they can claim the four-year regime on their foreign income and gains. This example is illustrative rather than advice, and their own figures would decide it.

First, treating the visa date as the date British tax starts.

Second, arriving with a portfolio nobody reviewed, then discovering what Britain makes of American funds.

Third, missing the four-year window because nobody mentioned it in year one.

Fourth, assuming American tax stops at the airport. It follows the passport, not the address.

Fifth, leaving a state filing obligation behind. Some American states keep asserting a claim long after the federal position has settled.

We build the map before the move, source by source, so the first British tax year starts from a plan rather than a surprise. Where something has to be done before arrival, we flag it while there is still time.

The work sits alongside our treaty relief service, and our note on the statutory residence test covers the rule that starts the clock.

This article is general information, not personal tax advice. Talk to us before you book the move.