Your American 401(k) from a British address: withholding, access and the treaty

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

Your 401(k) does not move when you do. The account stays with its American provider, still growing tax-free, while you live in Britain. The first problem most people meet is not tax at all: it is a provider that dislikes overseas addresses.

Then comes 30% withholding on the first payment, and a treaty claim to stop it. So this guide starts with those mechanics, then sets out which country taxes what once the money actually moves.

Key takeaways

• Growth inside US retirement accounts stays sheltered while you live in Britain.
• Regular withdrawals from US retirement accounts are generally taxable where you live, so usually in the UK.
• A lump sum is generally taxable only in America under the treaty.
• Qualified Roth withdrawals stay tax-free on both sides of the Atlantic.
• US citizens remain taxable in America regardless, and rely on credits instead.

Why does the provider still withhold US tax?

Because the default rate for a payment to someone abroad is 30%. Your provider applies it unless you file a treaty claim, usually on Form W-8BEN. Per the IRS guidance on Form W-8BEN (opens in a new tab), the form certifies your residence and the treaty article you rely on.

Some administrators refuse treaty claims as a matter of policy. Others insist on a US address, which nobody living in Britain can honestly give. Where withholding happens anyway, you reclaim it by filing a US non-resident return, which takes months.

So ask the provider about its treaty process before you need the money. In our practice this single question saves more trouble than any other step in this article.

What practical problems come up first?

Address and access problems, long before tax ones. Many US brokers restrict accounts held by overseas residents, freezing new investments or closing the account entirely. Some refuse to post statements abroad, and others block online access from a British IP address.

So check your provider's policy on non-US residents early. Moving the account to a firm that welcomes overseas clients is far easier while everything is still open and operating normally.

What makes a Roth different?

A qualified Roth withdrawal is tax-free in America, and the treaty carries that exemption across. HMRC therefore does not tax it either, provided the withdrawal genuinely qualifies under US rules. That combination makes a Roth unusually valuable to someone living in Britain.

The qualification rules still apply, though. You generally need the account open for five years and to have reached 59 and a half. Keep the paperwork showing when the account opened, because proving the point years later is harder than it sounds.

What happens to these accounts when you die?

They pass under US rules, and the estate position surprises many families. US retirement accounts count as American assets for estate tax, and a non-citizen who is not domiciled there receives only a $60,000 exemption. The estate tax treaty often helps, but somebody has to claim it.

Beneficiaries then meet the US distribution rules. Most inherited accounts must be emptied within ten years, and each payment carries its own tax. A British beneficiary needs the same treaty analysis as the original owner, because the distinction between regular payments and lump sums still applies.

Britain may look at the same money again. Inheritance tax follows domicile and long-term residence rather than where the account sits, so both systems can reach it. Our guide to US UK inheritance tax explains how the two interact.

Can you still contribute while living in Britain?

Usually not. US retirement accounts need American earned income to receive contributions, and a British salary stops counting once the foreign earned income exclusion applies to it. Americans in Britain who use that exclusion therefore lose the ability to fund an IRA from their pay.

Claiming the foreign tax credit instead can preserve the option, because the income stays on the US return. That trade-off deserves its own calculation, since the choice between exclusion and credit affects other reliefs too.

Can you move the account to a UK pension?

No, and this is the question we hear most often. There is no tax-free transfer route from a 401(k) or IRA into a British scheme. Any attempt to move the money means taking a distribution first, with the tax that follows.

Consolidating within America is usually possible instead. Rolling an old workplace plan into an IRA often widens your investment choice and simplifies the paperwork, without triggering tax. It also removes the risk of losing track of a former employer's plan.

What is the treaty position on retirement accounts?

The starting rule is that a pension is taxable only where the recipient lives. So a UK resident drawing regular payments from a 401(k) or IRA is generally taxed by HMRC, not the IRS. The money leaves America without a second claim attached.

Two exceptions matter. Lump sums go the other way, taxable only in the country where the scheme sits. And anything exempt in its home country stays exempt in the other, which is what protects a qualified Roth withdrawal.

Regular payments follow the person. Lump sums stay with the scheme. That single distinction decides most of the planning.

How does HMRC tax a withdrawal?

As foreign pension income, taxed at your normal UK rates once the personal allowance is used. You report it through Self Assessment, on the foreign pages, converting each payment into sterling. Per the GOV.UK guidance on tax when you get a pension (opens in a new tab), overseas pensions fall into the same income tax bands as British ones.

The tax years rarely line up neatly. America runs to December, Britain to April, so a single year's withdrawals can straddle two UK returns. Keeping a simple running record of payment dates avoids an unpleasant reconciliation later.

What if you are also a US citizen?

Then America taxes you regardless of where you live, because the treaty's saving clause preserves that right. Your withdrawals therefore appear on both returns. Relief comes through the foreign tax credit rather than through an exemption in either country.

Getting the credit in the right direction matters. The country with the primary right to tax depends on the type of payment, and claiming the credit the wrong way round produces a bill that nobody owes. Our guide to Form 1116 and the foreign tax credit explains the mechanics.

How do you plan a withdrawal?

Decide the shape of the payment before you request anything, because the shape decides the country. Most US retirement accounts allow both regular income and one-off withdrawals, and the treaty treats the two quite differently. The steps below keep the treaty position clean:

1. Confirm whether you want regular payments or a single lump sum.
2. Check your provider's treaty claim process and its address rules.
3. File Form W-8BEN with the correct treaty article before requesting money.
4. Estimate the UK tax at your marginal rate for regular payments.
5. Time larger withdrawals across UK tax years where that lowers the rate.
6. Record each payment date and its sterling value as it arrives.
7. Report the income on the foreign pages of your Self Assessment return.

Anyone approaching 73 should also check the required minimum distribution rules, which force payments from most US retirement accounts once you reach that age.

A worked example

Take an illustrative example. A British engineer returns to Leeds after fifteen years in Seattle, holding $400,000 in a 401(k). He is not a US citizen, and he plans to draw an income from the account at 62.

Regular monthly payments are taxable in Britain, so he files a treaty claim and receives them without US withholding. He reports the sterling amounts through Self Assessment each year, paying UK tax at his marginal rate.

Had he taken the whole fund as one lump sum, the treaty would have handed taxing rights to America instead. The difference between those two choices, on that size of fund, runs well into five figures.

Do these accounts need UK or US reporting?

The account itself is American, so it is not a foreign account from the IRS perspective. For HMRC, it is your income that matters rather than the account, and only when payments actually arrive. There is no annual UK charge on growth inside the fund.

Holders who are also American should still check their wider reporting. Our guide to the US UK tax treaty covers which reliefs survive the saving clause and which do not.

The mistakes that cost the most

Almost all of these happen at the moment of drawing, when the decision is already hard to reverse:

• Requesting a payment before filing the treaty claim, then waiting months for a refund.
• Taking a lump sum without checking which country gains taxing rights.
• Assuming a Roth needs no records because it is tax-free.
• Trying to transfer a US plan into a UK pension and triggering tax.
• Ignoring a provider's letter about overseas residents until the account is frozen.
• Converting payments at year-end rates rather than the rate on each payment date.

State pensions and social security follow their own rules entirely. Our guide to Social Security and the UK State Pension covers that side of retirement.

How US UK Tax Accountants helps

We map your accounts against the treaty, prepare the withholding paperwork, and model the tax on each withdrawal shape. Our pensions service covers both countries in one engagement, with a fixed fee agreed first.

In our practice the best results come from planning the first withdrawal carefully. Once a payment leaves the account, the treaty outcome is already fixed, and options narrow sharply.

Plan your first withdrawal

If you hold US retirement accounts and live in Britain, a short review before you draw protects the treaty position. Tell us what you hold and what income you need. You can book a consultation and hear back within one working day.

Last reviewed 12 September 2026 by the US UK Tax Accountants Tax Team. This article is general information, not personal tax advice — speak to a qualified US/UK tax adviser about your own position.

For the neighbouring question, Sent to America for work: the tax rules behind a US secondment walks through it in detail.