I moved to London last year and my S corporation has retained all its profits since. The IRS taxed me on those profits. HMRC has taxed me on nothing. Is that a good outcome?

It looks like a good outcome and is often the opposite. You have paid US tax in a year in which HMRC assessed nothing, so there was no UK liability against which to credit that US tax. When the company eventually distributes those profits, HMRC will tax the distribution as a dividend from a foreign company, and by then the US tax has been paid in a closed year on income HMRC characterises differently. Unless a deliberate distribution pattern is put in place, the retained profits are effectively a stockpile of future UK tax with no matching credit.

Can I simply make an election to have the S corporation treated as transparent for UK purposes?

There is no UK election that mirrors the US check-the-box regime for an entity that is already a corporation under its governing law. HMRC's classification analysis looks at the characteristics of the entity itself, principally whether it issues share capital, whether it has separate legal personality, and whether profits belong to the entity or to the members as they arise. A US corporation that has made an S election under the Internal Revenue Code remains a corporation for all non-tax purposes, and HMRC's published position, set out in its international manuals on GOV.UK, reflects that. The S election is a US federal tax election, not a change in the entity's legal form, and HMRC treats it accordingly.

My accountant says the treaty solves this. Does it?

The treaty resolves residence and allocates taxing rights, and it contains provisions addressing certain fiscally transparent entities, but it does not force HMRC to adopt the US characterisation of an S corporation or to grant relief for tax paid in a different year on differently characterised income. Credit relief under the treaty and under domestic UK rules generally requires the same income in the hands of the same person over a matchable period. Where the IRS taxes flow-through profits in one year and HMRC taxes a dividend in a later year, the treaty does not by itself bridge that gap. It can help at the margins, and the mutual agreement procedure is available, but it is not a substitute for planning the structure before you become UK resident.

Would revoking the S election and running the company as a C corporation improve things?

It can, because it aligns the two systems on the same fact pattern. A C corporation pays US corporate tax on its profits and the shareholder is taxed on dividends when paid, which is much closer to how HMRC already sees the entity. The shareholder-level US and UK taxes then arise on the same event in broadly the same period, which is what credit relief needs. The cost is a US corporate layer of tax that the S election was designed to avoid, plus the practical consequences of revocation, including a period during which a fresh S election may not be available. The comparison is not simply which structure has the lower headline rate but which produces creditable tax in matchable periods.

I am on the remittance basis. Does that fix the timing problem?

It changes the problem rather than fixing it. To the extent a distribution is not remitted, there may be no immediate UK charge on it, but the underlying US tax has still been paid on the flow-through profits in an earlier year, and a later remittance may bring the amount into UK charge long after any credit could be claimed. The remittance basis also carries its own costs and interacts with the treatment of employment income and gains from the same company. Recent and ongoing changes to the UK's rules for non-domiciled and internationally mobile individuals mean the analysis should be run against the regime in force for the year concerned, using current HMRC guidance on GOV.UK rather than assumptions carried over from an earlier era.

What should I do first if I already hold an S corporation and I am now UK resident?

Establish the position rather than the plan. Reconstruct which years the IRS has taxed flow-through profits, what has actually been distributed and when, how much accumulated profit sits in the company, and what you have already reported to HMRC. That gives you the size of the exposure and shows whether the immediate risk is a stranded credit, a misreported distribution, or both. Only then is it worth evaluating the structural options, because each of them, distribution patterns, revocation, salary calibration, or a change of holding structure, is a different answer depending on the numbers. Take advice from someone who is competent on both sides before you make any election or move any cash, because several of these steps are difficult or impossible to reverse.

The S-Corporation Mirror: HMRC vs IRS Treatment

If you are UK resident and you own a US S corporation, the two tax authorities are almost certainly taxing you on different income, in different years, under different characterisations, and the foreign tax credit machinery that is supposed to prevent double taxation may not connect them at all. The IRS looks through the S election and taxes you personally on your share of the company's profits as they arise, whether or not a penny leaves the corporate bank account. HMRC does not follow that election. It looks at the entity itself, sees a corporation with share capital and separate legal personality, treats it as opaque, and taxes you only when the company actually distributes. The result is that US tax lands in year one on trading profit and UK tax lands in year three on a dividend, and credit relief generally requires the same income to be taxed by both authorities in a matchable period. When it is not, the credit is stranded and the double taxation is real. The resolution is not a clever claim filed after the fact. It is structural: you either align the two events by controlling distribution timing, or you change the entity's US characterisation so that both systems tax the same thing at the same moment. Both decisions have to be made before the mismatch accumulates, because once the US tax has been paid in a closed year, there is very little left to fix.

Why does everyone know about Anson but nobody plans for the mirror?

The cross-border profession has spent more than a decade litigating and re-litigating the treatment of US LLCs in the hands of UK residents. The Anson litigation, which reached the UK's highest court, asked whether a UK resident member of a Delaware LLC was entitled to credit for US tax paid on the LLC's profits, and turned on whether the member had an entitlement to the profits as they arose or merely a right to distributions once declared. The case generated an enormous volume of commentary, HMRC issued a guidance response, and every competent adviser now knows to ask the question when an LLC appears on a client's balance sheet.

The S corporation is the same problem viewed from the other side of the mirror, and it receives a fraction of the attention. The reason is partly cultural. The LLC arrives in a UK adviser's office looking foreign and ambiguous, so it gets scrutinised. The S corporation arrives looking like a company, because it is one, and the UK adviser classifies it in about four seconds as an opaque foreign corporate, which is very likely correct. The problem is not that the classification is wrong. The problem is that the classification is right, and nobody follows the consequence through to what the IRS is simultaneously doing to the same client on the same profits.

There is also a founder-side reason. The S corporation is marketed in the United States as the simple structure. It is what the accountant recommends to the successful consultant, the agency owner, the professional practice. It avoids the corporate layer of tax, it permits a rational split between salary and distribution, and its compliance burden is modest by American standards. A founder who has been told for years that his structure is the straightforward one has no reason to raise it when he mentions, almost in passing, that he is moving to London.

What exactly does each authority think it is taxing?

Take the two systems separately, because the trap only becomes visible when you lay them side by side. On the US side, the S election under the Internal Revenue Code causes the corporation to be disregarded as a taxpayer for most federal income tax purposes. The company files an information return, allocates its items of income, gain, loss and deduction among its shareholders according to their stock ownership, and each shareholder reports his allocated share on his personal return. The allocation happens whether or not there is a distribution. A shareholder whose company earns profit and reinvests all of it in inventory, hiring, or a building has still been taxed by the IRS on that profit. The IRS explains the mechanics of shareholder allocation and basis on IRS.gov, and the point that matters here is that the charge is triggered by the earning of profit, not by its payment out.

On the UK side, HMRC's entity classification analysis does not care what election the shareholder has made with a foreign revenue authority. HMRC asks whether the entity has separate legal personality, whether it issues something in the nature of share capital, whether the profits belong to the entity when they arise or to the members, and how the entity's business is carried on. A US corporation that has made an S election answers those questions exactly the way an ordinary corporation does, because that is what it is under the law of its state of incorporation. The S election changes nothing about the entity's legal form. HMRC's approach to classifying overseas entities is set out in its international manuals on GOV.UK, and the ordinary conclusion for an S corporation is that it is opaque.

An opaque foreign company does not attribute its profits to its shareholders as they arise. It pays them out, or it does not. When it does, the UK resident shareholder has received a dividend from a foreign company, taxable in the year of receipt at the rates applicable to dividend income. When it does not, HMRC has nothing to tax, subject to the anti-avoidance provisions discussed further below.

How does the mismatch actually strand a credit?

Foreign tax credit relief, whether under the UK's domestic unilateral rules or under the double taxation treaty, is not a general-purpose subsidy for having paid tax somewhere else. It is a targeted mechanism with conditions, and the conditions are what fail here. Broadly, relief requires that the foreign tax was properly payable, that it was paid by or on behalf of the same person, that it was charged on the same income or gain that the UK is charging, and that the two charges relate to a period that can be matched. Each of those requirements is doing work in the S corporation case.

The same person test is usually satisfied and is therefore the one that lulls advisers into a false sense of security. The IRS taxes the shareholder personally on the flow-through profit, and HMRC taxes the same shareholder personally on the dividend. There is no entity-level tax being pushed onto an individual, which is exactly the issue that made the LLC cases difficult, so this element looks clean.
The same income test is where the analysis begins to break. The IRS has taxed a share of the corporation's trading profit, allocated by reference to stock ownership. HMRC is taxing a distribution declared out of the company's accumulated reserves. These are different receipts with different legal characters arising under different legal events, even though the money originated in the same commercial activity.
The timing requirement is where it breaks conclusively. Credit relief operates within a tax year. UK tax on a dividend received in one year cannot ordinarily be relieved by US tax paid on flow-through profit in a much earlier year, because there was no UK liability in that earlier year to relieve, and the US tax has since been paid in a US year that is closed. There is no general mechanism to carry a foreign credit forward across years and across a change of character to meet a later UK charge.
The character mismatch compounds the timing failure even where the years happen to coincide. Where a company distributes all of its profit in the same year it earns it, the US charge is on trading income and the UK charge is on dividend income. That coincidence of years helps considerably in practice, but it is not automatic that the two charges are treated as being on the same income, and the analysis is fact-specific.
The direction of the treaty's relief provisions matters. The treaty allocates primary taxing rights and requires the residence state to relieve, but where the two states have characterised the underlying arrangement differently at the entity level, the article that would deliver the relief may simply not engage on the facts the taxpayer presents.

The practical outcome is a founder who has paid substantial US tax on profits he never received, and who will later pay UK tax on distributions of those same profits, with nothing linking the two. He was not aggressive. He did not plan into a structure. He simply moved countries holding an entity that two revenue authorities describe in mutually incompatible terms.

Does the salary and distribution split make it better or worse?

The S corporation's defining planning feature in the United States is the split between reasonable compensation and residual distribution. The shareholder-employee takes a salary, which bears employment taxes, and the balance of the profit flows through as an allocated share that does not. Every American S corporation owner has had this conversation with his accountant, and the whole architecture of the structure is built around getting the split right.

Once the owner is UK resident, that architecture works against him. The salary component is comparatively well behaved: it is employment income to both authorities, it arises in the same period on both sides, and although there are questions about where the duties are performed and how the social security position is handled under the applicable agreement, it is at least income that both systems recognise as the same thing at the same time. It is the component most likely to attract clean credit relief.

The distribution component is precisely the part that breaks. It is the flow-through allocation that the IRS taxes on arising and HMRC ignores until payment. So the more successfully the owner has optimised his US position by minimising salary and maximising distribution, the larger the portion of his income that sits in the mismatched channel. The optimisation that made sense in Chicago is the thing that creates the stranded credit in Chelsea, and it is entirely invisible to the accountant who set it up, because from a US perspective nothing has changed at all.

What about the UK anti-avoidance rules sitting behind all of this?

It would be a serious error to conclude from the above that retaining profits inside the S corporation is a UK deferral strategy. The UK has a long-standing and broad body of provisions addressed to precisely this behaviour, and they operate independently of the classification analysis. The transfer of assets abroad code can attribute the income of a person abroad to a UK resident individual who has power to enjoy it, subject to the statutory exemptions. The rules on close companies and their overseas equivalents, the attribution provisions for closely-held non-resident companies, and the various charges on benefits provided by such companies all sit in the background and can apply on the right facts.

That produces the worst version of this problem. It is entirely possible to construct a fact pattern in which the IRS taxes the flow-through profit on arising, a UK attribution provision brings some part of the same profit into UK charge on a basis that does not align with the US charge, and the eventual distribution is taxed again as a dividend without full relief. The client is then not merely double taxed but taxed on a schedule that no adviser designed and no authority intended. These provisions are technical and heavily fact-dependent, and the correct response to any suspicion that they are in play is a proper analysis against current HMRC guidance on GOV.UK, not a rule of thumb.

What can actually be done about it?

There are real answers, but they are structural and they are time-sensitive. The one thing that does not work is filing a claim after several years of mismatch and hoping that the treaty rescues the position.

Align the distribution with the allocation. If the company distributes its profit in the same period the IRS allocates it, the two charges at least arise in matchable years, which is the single largest improvement available and requires no change to the entity. It costs the founder the ability to retain working capital inside the company, which for a growing business may be intolerable, and it needs to be operated deliberately every year rather than remembered occasionally.
Reconsider whether the S election should survive the move. Revoking it produces a C corporation, which pays US corporate tax and distributes dividends, and which HMRC and the IRS then broadly agree about: a company that pays tax on its own profits and shareholders who are taxed on what they receive. That symmetry is the whole point. The cost is the corporate layer of tax and the practical consequences of revocation, and the comparison must be run on the client's actual numbers rather than on headline rates.
Calibrate the salary component upward where the facts genuinely support it. Employment income is the part of the package that both systems recognise identically and in the same period, so shifting the mix toward it narrows the mismatched channel. This must respect the US reasonable compensation standard, the UK's own rules on the taxation of employment income, and the social security position under the applicable agreement, so it is a genuine analysis rather than a lever to be pulled.
Consider the position of the shares themselves, not just the income. An S corporation has strict eligibility requirements as to who may hold its stock, and a change of the shareholder's residence, or an attempt to interpose a holding vehicle or a trust for UK planning reasons, can inadvertently terminate the election with consequences that dwarf the problem being solved. Any UK structuring around the shares must be checked against those eligibility rules first.
Deal with the accumulated position before it grows. Every year of retained profit adds to a stock of earnings that has already borne US tax and has not yet borne UK tax, and each of those years is a future UK dividend charge with no credit behind it. The exposure is cumulative and quantifiable, and it should be measured before any decision is taken, because the size of the accumulated stockpile often determines which of the options above is viable.

What should an adviser take from this?

The lesson generalises well beyond the S corporation. Entity classification is not a filing detail settled once by whichever adviser happened to open the file. It is the foundation on which the credit relief position stands, and where two authorities classify the same entity differently, the credit machinery that both systems rely on to prevent double taxation can quietly fail while every individual return remains technically correct. Nobody makes a mistake. The IRS applies its own law properly, HMRC applies its own law properly, the taxpayer files accurately in both jurisdictions, and the result is double taxation that no one authorised.

The diagnostic question is therefore not whether the client's returns are right. It is whether the same income is being taxed by both authorities in a period the credit rules can match. If the answer is no, the returns being right is precisely what guarantees the problem. That question should be asked at the point of the move, not at the point of the first distribution, because almost every effective response requires action while the mismatch is still prospective. Once the US tax has been paid in years that are closed and the reserves have accumulated, the founder holding the simple pass-through he was sold has an expensive problem and very few remaining moves.