Roth Conversions While UK Resident: The Treaty

A Roth conversion moves money from a traditional IRA or a 401(k) into a Roth account: you pay US income tax on the amount converted now in exchange for tax-free qualified withdrawals later. The US side is settled — the converted amount goes into your gross income for the year you convert. The UK side, if you are UK resident when you convert, is genuinely unsettled: HMRC has published nothing that addresses Roth conversions, and the answer turns on whether a conversion is a payment from a pension scheme for UK purposes.

This article explains the tax treatment. It is not investment advice, pension advice, or a recommendation to convert or not to convert, and every conclusion below depends on individual facts.

Key takeaways

• US position, clear. Per IRS Publication 590-A, you "must include in your gross income distributions from a traditional IRA" that would have been taxable had you not converted them. Conversions made in 2018 or later cannot be recharacterised.
• UK position, unclear. No HMRC manual page addresses Roth conversions. The strongest argument that no UK charge arises rests on Article 18(1) and on the fact that nothing is paid out to you.
• Roth IRAs are expressly pension schemes under the treaty. The Exchange of Notes to the 2001 Convention names "Roth IRAs under section 408A" within the Article 3(1)(o) definition — a significant and under-used point.
• The saving clause matters enormously. Article 1(5)(a) protects Article 17(1)(b), 17(3), 17(5) and Article 18(1) and 18(5) from the saving clause in Article 1(4). It does not protect Article 17(2), the lump-sum paragraph.
• Timing is the quiet risk. The US taxes on a calendar year; the UK year runs 6 April to 5 April, and Article 24(4) gives credit only against UK tax "computed by reference to the same profits".
• Two separate five-year clocks apply to Roth withdrawals, counted differently.

What a conversion is, and why people do it

In US terms, a conversion is a distribution from a pre-tax retirement account immediately contributed to a Roth account. Publication 590-A sets out three permitted routes: receive a distribution and roll it over within 60 days; direct the traditional IRA trustee to transfer an amount to the Roth trustee; or, where one trustee holds both, direct that trustee to make the transfer. The last two are trustee-to-trustee movements — nothing passes through your hands.

The attraction is straightforward. You accelerate the tax bill to a year of your choosing, at a rate you can see, and the Roth then grows and pays out free of US tax if the conditions are met. People convert in low-income years, before required minimum distributions begin, or when a market fall has temporarily depressed the account value.

For a US citizen or green card holder living in the UK there is a second tax authority with a view, and that is where it becomes difficult. If you have not yet mapped how the UK treats your existing accounts, start with our guides to UK tax on a US 401(k) or IRA and the UK tax treatment of a Roth IRA.

The central question: does HMRC tax the conversion?

For the UK to tax a conversion, a UK charging provision has to bite. For a foreign pension the relevant machinery is Part 9 Chapter 4 of ITEPA 2003: section 573 applies to a pension "paid by or on behalf of a person who is outside the United Kingdom", and section 575(1) charges "the full amount of the pension income arising in the tax year".

Note the verbs. Both provisions are built around a payment that arises. On a trustee-to-trustee conversion nothing is paid to you, nothing is remitted to you, and you cannot spend a penny of it. The natural reading is that no pension income arises and there is nothing for section 573 to charge.

The treaty supports that reading. Article 18(1) provides that where a resident of one state is a member or beneficiary of a pension scheme established in the other, income earned by the pension scheme may be taxed as income of that individual only when, and to the extent that, "it is paid to, or for the benefit of, that individual from the pension scheme (and not transferred to another pension scheme)". A traditional IRA and a Roth IRA are both pension schemes for treaty purposes — the Exchange of Notes to the Convention lists, among US arrangements, "qualified plans under section 401(a)", "individual retirement accounts, individual retirement annuities, section 408(p) accounts, and Roth IRAs under section 408A". A conversion looks very much like a transfer from one treaty pension scheme to another.

And critically, Article 18(1) is one of the provisions protected from the saving clause. Article 1(4) allows a state to tax its residents "as if this Convention had not come into effect"; Article 1(5)(a) then disapplies that for, among others, "paragraphs 1 and 5 of Article 18 (Pension Schemes)". So the UK cannot use the saving clause to override Article 18(1) against its own resident.

That is a respectable position. It is not a certainty.

Why the other side of the argument is real

Three things keep this open.

First, US law characterises a conversion as a distribution. The IRS treats the amount as distributed and includible in gross income. A revenue authority looking at the same transaction can reasonably say that a payment occurred, even if its destination was another account.

Second, Article 18(1) speaks to "income earned by the pension scheme". That is the inside build-up. A converted balance mixes build-up and contributions, and the provision does not obviously reach the whole amount. Whether "and not transferred to another pension scheme" operates as a general exemption for scheme-to-scheme transfers, or only as a limit on taxing scheme income, is a question of construction no reported UK case has decided.

Third, and most dangerous, is HMRC's lump-sum test. INTM163160 states that for treaty purposes the term "lump sum" means "any non-periodic, irregular or abnormal payment of a pension", that a payment representing "50% or more of the total value of the pension fund" is a lump sum, and that "in most cases a payment of 20% or more of the fund is likely to be a lump sum". A full or large partial conversion fits that description precisely. If HMRC were to treat a conversion as a payment at all, it would land in lump-sum territory — and lump sums are governed by Article 17(2), which Article 1(5) does not protect from the saving clause. HMRC's own notes at DT19853 make the parallel point in the other direction: because Article 17(2) is not listed in Article 1(5), the US can tax a US citizen on a UK scheme lump sum under the saving clause. The same asymmetry can run against a UK resident.

⚠ This is an unsettled treaty position. Anyone presenting the UK treatment of a Roth conversion as free of doubt is overstating it. A position should be sized, documented, disclosed where appropriate, and reviewed by a licensed professional before any return is filed.

Does a Roth keep its tax-free character in the UK?

This is a different and much stronger question, and the answer is encouraging.

Article 17(1)(b) provides that the amount of any pension or similar remuneration "paid from a pension scheme established in the other Contracting State" that "would be exempt from taxation in that other State if the beneficial owner were a resident thereof" shall be exempt from taxation in the state of residence. HMRC applies exactly that logic to US retirement accounts: DT19853 states that a distribution from a US Individual Retirement Arrangement to a UK resident is exempt in the UK to the same extent that it would be exempt in the US.

A qualified Roth distribution is exempt in the US. A Roth IRA is a treaty pension scheme by name. And Article 17(1)(b) is expressly protected from the saving clause by Article 1(5)(a). That is three independent supports under one conclusion — considerably more than most cross-border exemption arguments can muster.

Two cautions. The exemption only reaches what is actually exempt in the US, so a non-qualified Roth distribution of earnings gets no help from it. And HMRC's manual speaks of IRAs generally, not Roth IRAs specifically; the step from one to the other is an inference, albeit a well-supported one.

The 25% mismatch, more precisely than it is usually put

It is often said that there is no UK equivalent of the 25% pension commencement lump sum for a US plan. That is too blunt.

ITEPA 2003 section 574A treats a lump sum paid under a scheme that is not a registered pension scheme, a relevant non-UK scheme or a UK employer-financed scheme as a "relevant lump sum", taxable as pension income. But Step 3 of section 574A(3) then provides that if the lump sum is paid under an overseas pension scheme, you deduct so much of the balance "as would, if the scheme were a registered pension scheme, not be liable to income tax under this Part", assuming all of the member's lump sum allowance and lump sum and death benefit allowance is available.

So a UK tax-free element can be available — but only where the US plan satisfies the UK statutory definition of an overseas pension scheme, which carries its own recognition conditions, and that is a question of fact about the plan's governing rules. Confirm against FA 2004 and the overseas pension scheme regulations whether the specific plan qualifies before relying on Step 3.

The timing trap: no US tax left to credit

This is the practical risk that catches people, and it has nothing to do with construing the treaty.

Suppose HMRC does assert a charge. Relief then depends on foreign tax credit, and Article 24(4) allows US tax on US-source income only as "a credit against any United Kingdom tax computed by reference to the same profits". Two mismatches can break that.

• The years do not line up. The US taxes on the calendar year; the UK tax year runs 6 April to 5 April. A February conversion falls in one US year and in a UK year ending weeks later, while the US liability is not finally determined until the following calendar year's return. Matching the credit to the right UK year requires apportionment. HMRC's current practice on apportioning US tax across straddling UK tax years should be confirmed before a claim is made.
• Saving-clause tax is not creditable by the UK. DT19853 records that the UK "will not provide relief for the US tax imposed on its citizens resident in the UK" where that tax arises solely under the saving clause in Article 1(4), by virtue of Article 24(6)(b); the US gives credit instead. Getting that sequence wrong is how a conversion ends up taxed twice in substance even though both systems contain relief.

State tax

Treaties bind the federal government, not the states. Article 2(3)(a) lists the covered US taxes as "the Federal income taxes imposed by the Internal Revenue Code (but excluding social security taxes)" and certain federal excise taxes. State income tax is outside the Convention.

So if you still have a filing connection to a US state — and some states are slow to accept that a move abroad has ended residency — a conversion can draw a state charge that no treaty article touches and that the UK will not necessarily credit. Check the position state by state for the year of conversion.

The two five-year rules

These are frequently conflated, and they are not the same.

The qualified distribution clock. Per Publication 590-B, a qualified distribution is one made after the five-year period beginning with the first tax year for which a contribution was made to a Roth IRA set up for your benefit, and made on or after the date you reach age 59½, because you are disabled, to a beneficiary or your estate after your death, or meeting the first-home requirements subject to a $10,000 lifetime limit.

The conversion recapture clock. Separately, a distribution of converted amounts "within the 5-year period starting with the first day of your tax year in which you convert an amount" generally attracts the 10% additional tax on the part of the converted amount that you had to include in income — the recapture amount. Publication 590-B is explicit that this period "isn't necessarily the same as the 5-year period used for determining whether a distribution is a qualified distribution", and each conversion has its own clock.

Why this matters cross-border: a non-qualified distribution is taxable in the US, so Article 17(1)(b) cannot exempt it in the UK. Converting and then needing the money inside five years can produce US tax, a US additional-tax charge and a UK charge with an awkward credit position, all at once.

Who this suits, and who it does not

It may be worth modelling where:

• You are in a genuinely low-income year — a career break, a loss year, a year between assignments — and the US marginal cost is unusually low.
• You intend to remain outside the US and draw on the account as a UK resident, so the Article 17(1)(b) exemption on the way out is the point.
• The slices are small enough not to look like a "lump sum" on HMRC's indicators, and a staged programme over several years is feasible.
• You are not yet UK resident. Converting before a move removes the entire UK question — see our note on pre-arrival tax planning before moving to the UK.

It is likely to be a poor idea where:

• You will need the converted money inside five years.
• You have a live US state filing connection that would charge the conversion.
• The conversion would be large relative to the fund and you could not fund a possible UK charge from other resources.
• You are close to returning to the US, so the UK risk is being run for no UK benefit.

What a defensible file looks like

1. Establish UK residence status and, where relevant, split-year treatment for the year of the intended conversion.

2. Confirm in writing that both the source plan and the destination Roth are treaty pension schemes, citing the Exchange of Notes.

3. Use a trustee-to-trustee or same-trustee transfer, never a 60-day indirect rollover — the latter puts money in your hands and badly weakens the argument that nothing was paid to you.

4. Size the conversion against HMRC's lump-sum indicators, and model the US federal cost, any state cost, and a downside case in which the UK charges the conversion with imperfect credit.

5. Document the treaty position with its paragraph references, consider whether disclosure on the UK return is appropriate, and record both five-year clocks from the outset.

Sources

• IRS Publication 590-A — conversion methods, inclusion in gross income, no recharacterisation from 2018
• IRS Publication 590-B — qualified distributions, both five-year periods, the 10% additional tax and recapture
• IRS: Roth IRAs — contributions are not deductible; qualified distributions are tax-free
• 2001 UK/USA Double Taxation Convention as amended by the 2002 Protocol — Articles 1(4), 1(5), 2(3), 3(1)(o), 17, 18 and 24, and the Exchange of Notes naming Roth IRAs
• HMRC DT19853, USA: notes — Article 17(1)(b) applied to US IRA distributions; saving-clause relief under Article 24(6)
• HMRC DT19852, USA: treaty summary
• HMRC INTM163160, Pensions – Lump Sums
• ITEPA 2003 Part 9 Chapter 4 — sections 573 to 576
• ITEPA 2003 section 574A — relevant lump sums and the Step 3 reduction
• HMRC: Self Assessment deadlines — UK tax year dates

When to get help

A Roth conversion while UK resident is one of the few cross-border decisions where the honest professional answer is "it depends, and part of it is unsettled". That is not a reason to avoid it. It is a reason to do it deliberately, with the downside priced before you press the button rather than discovered on a UK return.

We work as US and UK tax specialists on exactly this kind of position: modelling both outcomes side by side, sizing a staged conversion where one makes sense, and writing up the treaty analysis so it stands up if it is ever questioned. Every filing is reviewed and signed off by a licensed professional — an IRS Enrolled Agent who is also ACCA-qualified — and we will tell you plainly where a position is arguable rather than settled. If that is where you are, book a consultation.