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401(k), Traditional IRA, Roth IRA and US Social Security Tax Advice
If you live in the UK and receive pension income from the United States, the tax treatment is not always straightforward. A 401(k), traditional IRA, Roth IRA, US annuity, US Social Security payment or government pension may all be described loosely as “US pension income”, but they do not all follow the same UK tax rule. In many cases, the UK–US double tax treaty changes the result, and the type of payment you take can matter just as much as the type of pension you hold.
For most UK residents, the starting point under UK domestic law is that foreign pension income is taxable in the UK in the normal way. HMRC states that, from 6 April 2017, 100% of a foreign pension received by a UK resident is taxable in the UK under normal income tax rules, subject to any treaty protection or specific exemption that applies. That means you should not assume a US pension is outside UK tax simply because it arose overseas or because you paid into it while working in America.
Where the position becomes more technical is the treaty. The UK–US treaty contains separate rules for private pensions, Social Security, lump sums and government service pensions. It also includes a special exemption rule for amounts paid from a pension scheme that would have been exempt from tax in the country where the scheme is established. That is why generic online guidance is often wrong or too simplistic.
When UK tax applies to US pension income
If you are UK tax resident, the UK will usually look first at whether the payment is foreign pension income taxable on you as a UK resident. That is the broad domestic-law starting point. The next question is whether the UK–US treaty changes that position by giving exclusive taxing rights to one country, or by preserving an exemption for part of the payment.
For ordinary pension income, the treaty generally points to taxation in the country where you are resident. HMRC’s treaty manual says Article 17 provides for pensions and similar remuneration to be taxed only in the state of residence of the beneficial owner. So, for a UK resident receiving periodic income from a US private pension scheme, the UK will often be the main taxing country under the treaty.
That does not mean every payment is fully taxable in the UK without qualification. Article 17 also says that where the payment comes from a pension scheme established in the other country, any amount that would be exempt from tax there if the individual were resident there must also be exempt in the country of residence. HMRC specifically applies that principle to US IRAs.
How the UK usually treats a US 401(k)
A US 401(k) is generally treated as a pension scheme for treaty purposes. The treaty materials include US section 401(a) qualified plans within the relevant pension scheme definition. That means a UK resident drawing periodic retirement income from a US 401(k) is normally within the treaty pension rules, not outside them.
In practice, that usually means the UK taxes the payment as pension income, because UK domestic law generally taxes foreign pensions received by UK residents and the treaty usually points ordinary pension income to the country of residence. What is not correct is the idea that a 401(k) is automatically tax free in the UK because it is an overseas pension. HMRC’s published guidance does not support that.
How the UK usually treats a traditional IRA
Traditional IRAs need more careful analysis. HMRC’s treaty manual says that a distribution from a US IRA to a UK resident is exempt in the UK to the same extent that it would be exempt from tax in the US if the recipient were resident there. That is a very important point because it means the answer is not simply “all taxable” or “all exempt”.
In other words, if part of a traditional IRA distribution would be exempt in the US under domestic US rules, the treaty can preserve equivalent treatment in the UK. This is why a technical review is often needed before reporting IRA withdrawals on a UK tax return. A blanket statement that all traditional IRA withdrawals are fully taxable in the UK is too crude for a serious advisory page.
How the UK usually treats a Roth IRA
Roth IRAs are often misunderstood in UK tax discussions. The treaty definition of pension schemes expressly includes Roth IRAs under section 408A. That means they are not ignored by the treaty and should not be analysed as if they were just ordinary offshore investment accounts.
The more accurate approach is to apply the treaty rule properly. If some or all of the payment would be exempt in the US if the individual were US resident, the treaty can require corresponding exemption in the UK. That is a much safer and more technically correct way to describe the position than saying, without qualification, that only the growth is taxable or that all Roth withdrawals are automatically tax free in the UK.
Why lump sums need separate advice
One of the biggest mistakes in cross-border pension planning is assuming that a lump sum is taxed in the same way as regular pension income. Under Article 17(2) of the UK–US treaty, a lump sum derived from a pension scheme established in one country and paid to a resident of the other country is taxable only in the country where the pension scheme is established. For a lump sum from a US pension scheme paid to a UK resident, that points to US-only taxation under the treaty.
That means the timing and structure of withdrawals can matter significantly. A series of smaller periodic withdrawals may not have the same treaty outcome as a single lump-sum distribution. For that reason, it is risky to take substantial withdrawals from a US pension while living in the UK without reviewing the treaty position first.
How US Social Security is taxed in the UK
US Social Security has its own treaty rule. Under Article 17, social security payments made by one country to a resident of the other country are taxable only in the country of residence. For a UK resident receiving US Social Security, the treaty points to UK-only taxation.
That makes Social Security different from some other forms of US-source retirement income, and it should be addressed separately on any serious tax advice page. If your income includes both US Social Security and withdrawals from a 401(k) or IRA, those streams should not simply be merged into one generic answer.
Government pensions are different again
Pensions for government service can fall under a different treaty article. HMRC’s guidance explains that some US government pensions, including certain armed forces pensions, remain within the government service rules rather than the ordinary pension article. In those cases, the taxing result can depend on the individual’s residence and nationality status.
That is another reason why a broad phrase such as “US pension income” is not enough on its own. Before advising on UK tax, the pension first needs to be classified properly.
Will US tax still be withheld?
Sometimes, yes. The IRS says distributions to nonresident aliens are generally subject to withholding unless a treaty withholding exemption applies. That means the legal treaty outcome and the way the payment is processed by the US payer are not always the same thing in practice.
So even if the treaty ultimately gives the UK the taxing right, US tax may still be withheld unless the payer has the correct nonresident and treaty documentation. Where too much US tax has been deducted, the solution may involve a US reclaim, a UK foreign tax credit claim, or both, depending on the facts.
Can you claim UK relief for US tax suffered?
Often, yes. Where the same income is taxed in both places in practice, the UK may allow Foreign Tax Credit Relief against the UK tax on that income, subject to the normal limits and treaty rules. In many cases that helps prevent genuine double taxation, although it is usually better to get the treaty position right upfront than to rely on later credit claims.
What this means in practice
If you live in the UK and receive money from a US pension, the answer is rarely as simple as “tax free” or “fully taxable”. The correct UK treatment depends on what type of pension it is, whether the payment is periodic income or a lump sum, whether part of the payment would be exempt in the US for a US-resident holder, whether any US withholding has been applied, and whether a treaty claim is needed.
That is why cross-border pension advice should be taken before large withdrawals, not after. Once a payment has been made in the wrong format or with the wrong withholding treatment, fixing the position can become slower and more expensive than planning it properly from the start.
How we help with UK tax on US pensions
Our Tax Advisors advise UK-resident individuals on the UK taxation of US pension income, including 401(k) withdrawals, traditional IRA distributions, Roth IRA planning, US Social Security reporting, foreign tax credit claims and treaty analysis. We review the pension type, the withdrawal type and the treaty position before advising how the income should be reported in the UK.
Where needed, we can also review whether the income appears to have been taxed correctly in the US, whether unnecessary withholding has been deducted, and whether the UK return should include a foreign tax credit claim or a treaty-based treatment. This is particularly important where the pension provider has used default NRA withholding rules without applying the correct treaty position.