Accountants for US and UK tax: how to choose one, and what to check.

Most accountants are domestic specialists, and there is nothing wrong with that. A UK chartered accountant who spends their working life in Self Assessment, residence and domicile is genuinely expert. So is a US CPA who files a thousand federal returns a year. Neither, on their own, is equipped for a person the two systems both claim.

The US taxes its citizens on worldwide income wherever they live, which is unusual — most countries tax residence, not citizenship. The UK taxes on residence. So an American living in London is inside both systems at once, and stays inside both until they stop being one of the two things. Nothing about that is exotic, but it does mean every figure has to survive being read twice.

The practical consequence is sequencing and consistency. A foreign tax credit on the US return is computed from UK tax actually paid or accrued. A UK claim can turn on a US filing position. Get those out of step and you have two internally consistent returns that contradict each other, which is worse than one late one.

That is the whole case for a cross-border practice, and it is narrower than most firms pretend. It is not that cross-border tax is mystical. It is that the join between the two returns has to belong to somebody.

Every cross-border firm argues that one firm is obviously better, and on their own pages that argument is never tested. So here is the honest version. Two good firms who talk to each other, share figures and agree the treaty position in advance will produce a better outcome than one mediocre firm that does both. The single-firm advantage is real but specific: it removes a handoff, and handoffs are where cross-border work goes wrong.

The failure mode with two firms is rarely incompetence. It is that each does its own job correctly, on its own timetable, using its own assumptions. The UK adviser finalises in January; the US adviser needed those numbers in March of the previous year and used an estimate. Neither is at fault, and the return is still wrong.

The failure mode with one firm is different: the firm is strong on one side and thin on the other, and the thin half is invisible to you because you cannot audit it. Some firms openly outsource the US return to a third-party provider. That is not disqualifying — it can be perfectly well run — but you should know whether it is happening before you engage, not afterwards.

So the question to ask is not "do you do both?" It is "who, by name, prepares each return, and who is accountable when the two disagree?" A firm that answers that crisply is telling you how it is organised. A firm that answers it with reassurance is telling you something too.

The IRS requires a PTIN for anyone who is paid to prepare a federal return, or who is paid to assist substantially in preparing one. It is not a qualification — obtaining one involves no examination — but it is a registration, it is annual, and its absence tells you the person is not set up to do this work for money.

Separately from preparation, there is the question of representation: whether the person can speak to the IRS on your behalf when something goes wrong. The IRS distinguishes unlimited from limited representation rights. Only attorneys, CPAs and Enrolled Agents have unlimited rights. A UK chartered accountant, however senior, has none.

This matters more than it sounds. A cross-border return is more likely than average to draw correspondence, because it contains elections, treaty claims and disclosure forms that a domestic return does not. The person who prepared it being unable to answer for it is a gap you discover at the worst moment.

So a UK firm advertising US returns is doing one of three things: employing or contracting someone US-credentialled, holding a PTIN without representation rights, or outsourcing. All three exist in this market. Ask which.

You appoint a tax agent by authorising them, and HMRC sets out how to appoint someone to deal with HMRC on your behalf. The authorisation route — historically the 64-8 form, now more often done digitally — is documented on GOV.UK. Nothing in it requires the agent to hold a UK credential.

The regulatory constraint sits elsewhere. Accountancy service providers must be supervised for anti-money-laundering purposes, by HMRC directly or through an eligible professional body. That is the UK equivalent of the PTIN question: a plain registration test, not a judgement about quality, and a firm that cannot answer it should worry you.

HMRC also publishes a standard for agents that applies to anyone representing a taxpayer, member of a professional body or not. It is worth reading precisely because it is short and because it describes conduct HMRC expects rather than conduct firms advertise.

One caution. Whether a particular US firm is properly set up to act in the UK is a fact about that firm, and the only way to establish it is to ask and then check. Do not infer it from a London phone number or a serviced-office address.

Competitor pages list these letters and stop. Nobody explains the difference between a qualification and a permission, which is the only part that changes what happens to you when the IRS or HMRC writes. The table below separates them.

Read the last column first. "Representation" is the right to act for you in correspondence, examination and appeals — to be the person the revenue authority talks to instead of you. It is the practical difference between an adviser who can fix a problem and one who can only explain it.

The IRS publishes a Directory of Federal Tax Return Preparers with Credentials and Select Qualifications, searchable by location and credential. It is the fastest single check available. It is not linked from this page because the directory host refuses automated requests and this site only publishes links it can verify are live — search its name on irs.gov and it is the first result.

The other checks are all linkable, and they are below as steps. None of them establishes that a firm is good at cross-border work. They establish that the person is who they say they are, which is a lower bar, and one that a surprising number of expat tax operations do not clear.

This is the part of the market that is genuinely harder to verify, and the research behind this page found that not one of roughly twenty ranking UK firm pages published an anti-money-laundering supervisor, a professional body registration number, or a complaints route. That is not evidence that those firms lack them. It is evidence that nobody is being asked.

So ask. A properly run UK practice can answer all of the following from memory, and a firm that treats the questions as an imposition has told you how it thinks about being accountable.

Very few firms publish anything. In the research behind this page, two of roughly twenty UK firm pages showed a number at all. That opacity is why the range looks irrational: a quote for one federal return and a quote for a federal return plus a state return plus FBAR plus two disclosure forms plus a Self Assessment are not the same product, and neither quote is wrong.

US UK Tax Hub quotes a fixed fee in writing after a free scoping call, and does not publish a rate card, so there is no price list to give you here. What is more useful is the list of things that actually move a fee, because you can use it on any firm.

One structural point. A percentage of tax saved is not a normal basis for tax compliance fees, and it misaligns the incentive at exactly the moment judgement matters. How we work sets out the basis this practice uses.

A fixed fee is a promise about scope, not about your life. When something outside the scope appears — a fund you forgot, a gift from a parent, a letter from HMRC — the honest response is to tell you what it costs before doing it. The test of a firm is not whether extras exist. It is whether you hear about them in advance.

Ask for the exclusion list in writing alongside the quote. Any firm that has one is organised; any firm that cannot produce one has not thought about your file yet.

This is the most operational question a dual filer has, and the research found it answered nowhere. It also cannot be answered with a flat rule, because the periods overlap rather than coincide. A single UK tax year straddles parts of two US ones.

The working order is therefore about dependency, not calendar. The UK residence position decides what the UK taxes at all. Once UK figures are known for the relevant months, the foreign tax credit can be computed on real numbers instead of estimates. Preparing the US return first usually means amending it once the UK position settles, which costs more than waiting did.

The exception runs the other way. Where the US return drives the outcome — an election being made, a US-source gain, a year where the Foreign Earned Income Exclusion is in play and the decision affects UK planning — the US analysis comes first and the UK return follows. This is a judgement per client, not a policy.

Deadlines make the sequencing workable rather than fraught, because the US side has more give than the UK side. The deadline calendar sets out both countries side by side.

The research found that outside one firm, nobody publishes what happens after an enquiry. That is a strange omission, because process is the thing a nervous buyer is actually asking about when they ask how much it costs.

This is the sequence this practice uses, described in more detail on how we work. The point of writing it down is that each stage has an artefact you can hold the firm to.

These are worth understanding because the differences are substantive and the names are not self-explanatory. Signing the wrong one leaves your adviser able to read your file but unable to defend it.

Note the asymmetry in the last row. Authorising a UK agent is an appointment; authorising US e-filing is per return, per year. A firm that asks you to sign an 8879 every year is doing it correctly.

Judgement questions — "are you good at this?" — produce reassurance. Factual questions produce information. These are the factual ones, in the order that tends to be most revealing.

Most of these are not subtle, and most of them are also the behaviours the IRS itself warns about. The reason they persist is that a frightened taxpayer who is several years behind is an unusually easy sell.

The honest starting point is that a filing obligation is not the same as a need for help. A US citizen abroad may well have to file even on modest income — and note that the married-filing-separately threshold is $5 of gross income, not the single-filer figure, which matters because filing separately is the usual status for a US citizen married to a non-US spouse. Having to file is not, by itself, a reason to pay someone.

What creates genuine need is interaction: a fund whose treatment differs between the two systems, a pension where the treaty has to be read paragraph by paragraph, a property sale taxed on different bases in each country, an unfiled year. Absent those, a careful person with good records and time can file correctly.

The filing obligation checker will tell you what is actually required in your case, for free, without talking to anyone. If the answer is a plain federal return and nothing else, that is a legitimate outcome, and there are also free routes: HMRC lists where to get help with tax, and GOV.UK sets out who must send a Self Assessment return.

Saying this on a commercial page costs us some enquiries. It is still the correct thing for a regulated practice to say, and a firm that will not tell you when you do not need it has told you something about how it will advise you when you do.

Both routes ask for 3 years of amended or delinquent returns and 6 years of FBARs, with a certification of non-wilfulness — Form 14653 on the Foreign route and Form 14654 on the Domestic one. The route you qualify for is a question of fact, principally about where you have been living, and it changes the cost of coming forward by a large margin.

The word "penalty-free" appears unqualified on competitor pages, and it is the single most consequential error in this market, because a reader on the Domestic route who believes it will make a decision on a false basis. Never accept it from any firm without the route named.

Both routes also close the moment the IRS makes contact about the years in question. That is what makes delay expensive rather than merely uncomfortable, and it is the honest reason to deal with it sooner.

A firm taking on a catch-up should be able to tell you, early, which route it believes applies to you and why. If it cannot, it has not yet looked at the facts that decide it.

The question is not whether software is capable. It is whether it asks you the right questions. A package built for a domestic filer will not ask whether your UK workplace pension is a trust for US purposes, or whether the fund inside your ISA is a passive foreign investment company, because a domestic filer has neither.

That is why the software failure mode is silent. It produces a return that looks finished and is internally consistent, with a disclosure form missing that nobody was ever prompted to consider. You find out years later.

A reasonable middle position: use the tools to work out what you are dealing with, then decide. The PFIC checker and FBAR threshold checker are free and will tell you whether your situation contains the things software handles badly.

Switching is normal and the mechanics are mostly administrative. Authorisations are the part people forget: a new UK agent has to be authorised with HMRC, and a US representative needs a fresh Form 2848 — the old firm's authority does not lapse simply because you stopped talking to them.

Ask the outgoing firm for prior-year returns as filed, computations, carryforward schedules and any elections made. The carryforwards matter more than people expect: unused foreign tax credits carry forward for years, and a new adviser who cannot see them cannot use them.

Timing is worth a thought. Switching immediately before a deadline means a new firm meeting it on unfamiliar facts. Switching just after one gives everybody the most useful thing, which is time.

The common triggers are an unexplained swing in tax between years, a treaty position you cannot account for, a disclosure form you suspect was missed, or an adviser who has become vague. None of these means anything is wrong. All of them are worth resolving before they compound.

A review should produce a written answer to three things: what position was taken, whether it was defensible, and whether anything should be amended. A reviewer who leads with amendment before establishing the first two is selling, not reviewing.

An amendment is not automatically the right answer even where an error exists. Materiality, the statute of limitations, interaction with the other country and whether the correction helps or hurts all bear on it. That is a judgement, and it should be explained to you as one.

It is worth being direct, because the market's implicit promise is that the right adviser makes the problem go away. Sometimes the answer is that both countries tax something, relief reduces the total but does not eliminate it, and the cheapest remaining option is still expensive.

Nor can an adviser undo the past. A fund bought three years ago was a PFIC when you bought it. A pension contribution made last year was made. Advice changes what you do next, which is why the highest-value hour in cross-border tax is almost always before a decision rather than after it.

And no adviser removes your own responsibility for your return. Authorising someone to act does not transfer that. It is worth knowing plainly rather than discovering it.

The organising idea is the join. One specialist stays on your file from the first call to submission, so the judgement made in year one is remembered by the person who made it in year three, and the two returns are built to agree rather than reconciled afterwards.

Fees are fixed and quoted after a free scoping call, with the scope written down and the exclusions named. There is no percentage of tax saved. If the scope genuinely changes you hear before the work happens. How we work sets out the four stages, and our team describes how the two halves of a file are staffed.

Apply the checks on this page to us as readily as to anyone else. Ask who is preparing each return, what they hold, who supervises the firm, and what the fee excludes. Those are ordinary questions and a practice worth hiring will answer them without friction.