Notes from the overlap between two tax systems.
Plain-English writing on the filings, thresholds and reliefs that come up most, and the assumptions that quietly cost people the most money.
The Child Trust Fund your American child cannot ignore
Children born in Britain between 2002 and 2011 have one, often forgotten. Where the child is also American, a tax-free British account can be a reporting problem waiting at eighteen.
The foreign-owned US LLC that files a return and owes no tax
A British founder sets up a Delaware LLC, never trades through it, and assumes there is nothing to file. There is, the penalty is $25,000, and it applies whether or not the company made a penny.
When a tax debt reaches your passport
A US tax debt above a threshold gets certified to the State Department, and the passport goes with it. For an American living in Britain that is not an inconvenience; it is the document their life runs on.
The reduction that used to cut your US Social Security has gone
For decades a British pension quietly reduced an American's Social Security. The provision that did it was repealed in January 2025, and the repeal reaches back further than most people realise.
Disclosing US income to HMRC: the British half of catching up
Americans in Britain know the US catch-up routes. Rather fewer know that HMRC has its own, that it runs on a 90-day clock, and that you calculate your own penalty.
Your first UK tax year: what the year of arrival actually taxes
Move to Britain in October and the UK tax year still began in April. Split year treatment can fix that, but only through one of the statutory cases, and only if the facts fit.
Bona fide residence or 330 days: which test should you use?
Two tests open the door to the foreign earned income exclusion. One counts days and the other weighs your life. Picking the wrong one costs a year of relief.
The dual-status year: half resident, half not, one return
Move to or from America part-way through a year and the return splits in two. Worldwide income for one half, US-source only for the other, and most of the usual reliefs switched off.
The foreign housing exclusion: two numbers people keep confusing
Rent in London is high enough that the foreign housing exclusion is worth claiming. It is also worth understanding, because the ceiling on qualifying expenses and the amount you can actually exclude are different numbers.
Form 8858: the return a UK sole trade quietly creates
An American freelancing in Britain files a Schedule C and thinks the business reporting is done. Form 8858 is the return nobody mentions, and the penalty for missing it starts at $10,000.
The certificate of residence: proof the treaty asks for
Treaty relief is not self-service. A foreign payer wants proof that Britain taxes you on the income, and HMRC issues that proof one certificate at a time.
Redundancy pay: tax-free in Britain, taxable in America
The first £30,000 of a redundancy package escapes UK tax. The United States has no equivalent exemption, so an American in Britain can owe tax on money that arrived free of it.
The Roth IRA that keeps working after you move to Britain
Most American tax breaks stop working the moment you land in Britain. HMRC's own manual suggests a qualified Roth distribution is the exception, and the reasoning is worth understanding before you rely on it.
Self-employment tax: the 15.3% the exclusion does not touch
The foreign earned income exclusion wipes out the income tax and leaves self-employment tax standing. For an American freelancing in Britain, the answer is a certificate of coverage.
UK dividends on a US return: the allowance that does not travel
Britain gives dividends their own allowance and their own rates. America gives them neither, unless they qualify, and the British allowance leaves nothing to credit against the American charge.
US LLC profits and a UK resident member: the mismatch nobody mentions
A US LLC is transparent for American tax and a company for British tax. The same profit can be taxed twice, and the relief most people assume is there often is not.
FIRPTA withholding: 15% of the price, not the profit
The buyer withholds on the gross price, not on your gain. Sell at a loss and the money still goes to the IRS, and you wait a year to get it back.
The foreign tax credit carryover nobody tracks
Unused credit does not vanish at the end of the year. It runs back one and forward ten. The problem is that it only exists if somebody writes it down.
Form 709: when giving money away becomes a filing
Helping a child buy a flat is not a taxable event for most Americans. It is often a reporting one, and the form is due with the return rather than later.
Form 8865: the filing a UK partnership brings with it
Joining a British LLP feels like an ordinary career step. For an American it can bring an annual US filing that nobody at the firm has heard of.
The $60,000 line: US estate tax for people who never lived there
A British family with US shares can cross the American estate tax threshold without anyone ever having set foot in the country. The line sits at $60,000.
Capital losses do not cross the Atlantic
A loss is a loss in both countries, but almost nothing else about it matches. The relief differs, the carry rules differ, and one of them expires if you say nothing.
Treaty-based return position: when Form 8833 is required
Most treaty claims need no disclosure at all. The ones that do are the ones where you are telling the IRS that the treaty beats the Code, and saying nothing is the expensive option.
Gift Aid after leaving the UK: the declaration that keeps running
A standing order set up years ago keeps attracting relief long after you stop paying the tax that justified it. The shortfall belongs to the donor, not the charity.
Does your British spouse need a US tax number?
Most British spouses of Americans never need a US tax number. The ones who do usually discover it halfway through a return, which is the worst moment.
Net investment income tax: the threshold that halves when you file separately
A surcharge most Americans abroad have never heard of, with a threshold that halves for exactly the filing status most of them use.
Charitable giving when you file in both countries
Generosity does not cross borders cleanly. A gift to a British charity usually earns British relief and nothing at all on the American side, and the treaty does not fix it.
New tax year: what resets on 6 April, and what to settle first
Some British allowances vanish at midnight on 5 April and some roll forward. Knowing which is which decides what deserves your attention in March.
Building a financial plan when two tax systems both claim you
Most cross-border mistakes are not technical. They happen because two competent advisers each optimise half a position, and nobody owns the join between them.
Year-end planning when your household has two year ends
Most households get one deadline to act before. A household inside both systems gets two, and the moves that help on one side can cost real money on the other.
File anyway. The penalty for not filing is the bigger one.
Both authorities separate the failure to file from the failure to pay, and they price them differently. Knowing which is which changes what you should do this week.
HMRC will ask what you can afford. Have the figure ready.
The conversation turns on affordability, not sympathy. Going into it with a worked figure is the difference between an agreement and a demand for the full amount.
The plan is the easy part. Paying it from a British bank is not.
Two routes exist, with published thresholds for applying online. The difficulty for someone living in Britain is rarely eligibility; it is how the money actually gets there each month.
Your tenant may have to deduct tax from the rent before you see it
Letting a flat after you emigrate puts your tenant or agent in the tax collection business. There is a way to be paid gross, and a separate American calculation waiting behind it.
One form tells HMRC you have gone. The rest of the year is the work.
The departure form is five minutes. The final year behind it involves two tax authorities, two calendars and a set of decisions best made before the removal van arrives.
The repatriation year has more filings than the year you emigrated
Emigrating is one country's paperwork. Returning is two countries' paperwork plus a state you have not filed with for years, in a year when the reliefs you relied on stop working.
Three dates decide the tax: leaving, arriving, and the contract
Nothing about the asset changes. The date of the contract decides which system taxes the gain, at which rate, and in which currency the profit is even measured.
Britain splits your year. The IRS does not, and that is the whole problem.
Britain can tax half your year while America taxes all of it. The relief is mechanical rather than optional, and it stands or falls on the evidence you kept.
Three years, six years, or forever, depending on what you did
The published periods are shorter than people fear and longer than people keep. A few documents matter for decades, regardless of what the retention rules say.
Six dates, two countries, and none of them line up
One tax year ends on 5 April and the other on 31 December. Everything downstream inherits that mismatch, including the deadline you are most likely to miss.
British trustees will not file an American form. You can file it for them.
The form belongs to the trust and the penalty belongs to you. That asymmetry is the whole problem, and the instructions contain its solution.
Form 3520, a stepped basis, and a house measured in the wrong currency
Receiving the house costs nothing in American tax. Selling it, letting it or holding it while the pound moves are the events that matter, and all three turn on one number fixed at the date of death.
A 1% excise tax, a quarterly return, and a trust nobody meant to create
Writing a policy in trust is standard British planning. For an American paying the premiums, it can add an excise tax, a quarterly return and a foreign trust to report.
Two legal systems, one estate, and a valuation everyone needs
An estate with assets on both sides of the Atlantic needs two administrations, and they run on different timetables. The documents that serve both are worth gathering once.
The trustees called it a loan. The IRS calls it a distribution.
British families use trusts routinely and sensibly. An American beneficiary turns that ordinary arrangement into one of the heaviest reporting burdens in the code.
Paid in March for work done last year, in a country you have left
Deferred pay is the one part of a package that reaches back into a year you have finished and a country you may have left. Both systems have rules for it, and they are not the same rules.
The relief every other American abroad relies on is the one you cannot use
Government service abroad has its own rules, and the headline one is a subtraction. The exclusion that shelters most expatriate salaries is closed to you.
Four income streams, four answers, and only one of them is expensive
Salaried hospital work is the easy part. Private practice is where an NHS doctor with American citizenship loses money, and it has nothing to do with income tax.
The treaty gives royalties to one country. Your passport gives them back.
Article 12 is one of the tidiest provisions in the treaty. For an American living in Britain, the saving clause unpicks it, and a different article puts it back together.
Four ways to be paid for the same code, and four different tax outcomes
The rate is the same and the work is identical. Whether you are inside IR35, outside it, on an umbrella payroll or invoicing a US client decides what you keep.
Your coins have an address for tax, and it is wherever you live
Holding tokens on an offshore exchange feels borderless. Both tax authorities disagree, and one of them decides location by looking at where you live.
Britain exempts the whole award. America asks what you spent it on.
The two systems ask different questions about the same award. Britain looks at who holds it. America looks at what it paid for, line by line.
The year a written-off loan became a tax question again
A temporary rule kept discharged education debt out of income for five years. It covered discharges before 2026, and the calendar has moved on.
Moving your own money is not income. Everything around it might be.
Nobody taxes a bank transfer. What surrounds one — a gift from a parent, a balance that crosses a threshold, a mortgage repaid in another currency — can still reach a return.
The treaty article that exempts visiting academics, and the citizens it leaves out
A two-year exemption for visiting professors sounds generous, and it is. Whether it reaches you depends on your passport rather than on your post.
Opening an account here is easy. Keeping the paperwork straight is the work.
The forms ask about citizenship and place of birth for a reason, and the answer sets off a chain that ends on your American return rather than at the branch counter.
Your American investments become a British tax question the day you land
The account does not change when you move. What changes is that a second country now taxes everything inside it, and the two systems disagree about what a fund even is.
Studying in Britain does not pause your American filing
A degree in Britain comes with a bank account, a part-time job and often a grant. Each of those has an American consequence, and the filing threshold is lower than most people assume.
Three conditions decide whether a short teaching trip is taxed here
Short academic postings look simple until someone counts days. The treaty test has three limbs, not one, and UK residence is decided somewhere else again.
The yearly average is a convenience, not the rule
Most people reach for the IRS yearly average table and stop there. The guidance actually starts somewhere else, and for one-off amounts it points the other way.
You use the NHS. The US still asks for Medicare tax.
American healthcare taxes do not stop at the runway. Here is which country collects, what the social security agreement with Britain settles, and where people still pay twice.
Your employer's health cover is taxed here and often ignored there
A benefit Britain taxes and America excludes sounds like good news. For a US citizen filing in both countries, it quietly rearranges the credit arithmetic instead.
Salary sacrifice works here. Your US return asks a different question.
Giving up pay for a pension contribution or a benefit is ordinary in Britain. For a US citizen it raises a treaty question, a reporting question and, occasionally, a bill nobody planned for.
Maternity pay in Britain, a filing question in America
Two British payments support new parents, and they behave differently in America. One arrives through payroll with tax deducted. The other arrives tax free, which is the one that causes trouble.
The benefit Britain does not tax can still land on your US return
Britain publishes a clear list of which state benefits it taxes. The US does not read that list. Where the two diverge, a payment can be tax free here and still belong on a US return.
You moved to London. California may not have noticed.
Leaving the country does not end California residency by itself. And a Californian who stays resident gets no credit for British tax at all.
The paper trail that proves you really left your state
States decide residency on the strength of your ties, and they read the record long after you have gone. The time to build that record is before you leave.
Leaving New York for London without leaving New York's tax net
New York keeps you as a domiciliary until you prove otherwise with clear and convincing evidence. Two narrow exceptions exist, and one was written for people abroad.
Which states keep a claim on people who have moved abroad
There is no official league table of states that pursue former residents. There are rules, and they differ in ways you can compare before you move.
Do you still need a state return when all your income is British?
The federal return follows your passport. The state return follows your residency, and for most people abroad the answer is either nothing at all or a surprisingly large bill.
You were born in America and left as a baby. The IRS still counts you.
Citizenship arrived with your birth certificate, and the filing duty came with it. Most people learn this from a bank letter, decades late.
Born in America, raised in Britain: what your US return actually looks like
The return is less frightening than the idea of it. Salary usually nets to nothing. Savings wrappers and funds are where the real work sits.
Why your British bank suddenly wants to know if you are American
The bank is not accusing you of anything. It is following an agreement between two governments, and a place of birth on its records is often enough to start it.
Filing your first American returns from Britain: what catch-up really involves
People expect five years of paperwork. The usual route asks for three returns and six account reports, posted together on paper, with the red ink in the right place.
Getting a Social Security number as an adult who has never lived in America
Nothing on the American side moves without it. The application is slow, strict about original documents, and for adults it means an interview in London.
Taking money from an American plan while living in Britain
The treaty gives regular payments to your country of residence and lump sums to the source country. Then the saving clause takes much of that back from citizens.
Tidying up pensions on two sides of an ocean
Nobody can merge a 401(k) with a SIPP. What people call consolidation across borders is really two separate tidying exercises, each with its own traps.
The form your British company hands the IRS
Incorporating in Britain is easy. The American paperwork that follows is not, and the penalty for skipping it starts at five figures before any tax is due.
The rule that taxes your company's profit before you take it
Profits left inside a British company were never safely parked. From 2026 the rule that reaches them has a new name, a smaller deduction and one fewer escape hatch.
The overseas pension transfer that rarely suits an American
No American scheme appears on HMRC's list, a 25% charge now catches most European destinations, and the IRS has already ruled on the most popular one.
Moving to Britain for the last chapter, and what it costs
Two systems, four income sources and a treaty that answers each one differently. The pieces are knowable, and almost nobody assembles them before the move.
Paying yourself from a company two countries can see
British advice splits the two on rates alone. American rules treat one as earned income and the other as investment income, and that single distinction moves the answer.
A British pension, an American return, and one treaty paragraph
One paragraph of the treaty covers social security, and it survives the saving clause. Whether it helps you depends entirely on which country you live in.
Incorporate, or stay as you are? The American version of the question
British advice says incorporate once profits pass a certain point. American rules add reporting, a current charge on retained profit and a five-year election. The answer moves.
The British tax that has nothing to do with your profits
VAT is not a tax on profit, so a loss-making business can owe it. The threshold arrives faster than founders expect, and the deadline to react is thirty days.
Claiming child benefit when one of you earns too much
Above a certain income the payment gets taken back through the tax system. Opting out entirely is usually the wrong answer, and it can cost a parent their pension record.
Separating across two tax systems, and the rules that differ
Splitting assets is usually tax-free between spouses. That protection has an expiry date in Britain, and a hole in America when one of you is not American.
Paying school fees across an ocean, and who gets taxed on it
Grandparents helping with fees is generous and ordinary. Doing it across a border turns it into a gift question, a reporting question, and occasionally a tax bill.
Sending money home to your parents, and what the IRS makes of it
Monthly transfers to a parent overseas feel like they should count for something. On an American return they usually count for nothing at all.
Your baby may be American. Here is what that actually means.
Citizenship can pass to a child born here without anyone applying for it. The paperwork is easiest in the first year and hardest at eighteen.
Fixing a filed US return without making the position worse
Correcting one figure on a filed return is routine. Using the same form to fix years of missing filings is the mistake that removes your better options.
The brown envelope: what an HMRC enquiry actually involves
A letter saying HMRC is checking your return is alarming and usually routine. Knowing the limits on what it can cover makes the whole thing considerably smaller.
How far back the IRS can reach, and when the clock never starts
People assume old years eventually go quiet. Some do. A year with no return filed, or a missing foreign form, can stay open indefinitely.
The quiet fix that makes an IRS problem louder
Filing the missing years quietly feels discreet and sensible. It removes the protection the formal routes give you, and it cannot be undone once the returns land.
The penalty defense that works, and the one that never does
The IRS will remove penalties for someone who took ordinary care and still could not comply. It decides on the facts, so the facts are what you have to supply.
Quarterly payments to the IRS when you live on another continent
Nobody withholds tax from a freelance invoice or a foreign salary. The IRS still expects to be paid through the year, four times, on its own schedule.
Going freelance in Britain when the IRS still counts you in
Registering as self-employed here takes ten minutes. The American half of the job takes rather longer, and one certificate decides how much you pay.
IR35 for the American contractor: who decides, and what it costs
Contract through a limited company and one question follows you: would this be employment without the company? The answer decides the tax, and often somebody else gives it.
One business, two sets of accounts, and how to make them agree
The same invoices, the same expenses, and two profit figures that refuse to match. Most of the difference is explainable, and all of it is manageable.
Setting up a British company when the IRS owns a share of your thinking
Forming one takes an afternoon and costs less than a dinner. The American consequences arrive every year afterwards, whether or not you take money out.
Buying your first UK home with an American passport
Nothing stops an American buying a home here. What changes is the second set of records the purchase quietly starts, and the sale it sets up years later.
Sharesave, SIPs and EMI options when you also answer to the IRS
HMRC approval takes the income tax out of a Sharesave or EMI option. The IRS never approved anything, so it taxes the same benefit on its own timetable.
Your sterling mortgage and the tax gain you never saw
You borrowed pounds and repaid pounds. The IRS measures both in dollars, and the difference can be a taxable gain nobody warned you about.
The Lifetime ISA bonus looks like free money. The IRS has questions.
The government tops up every pound you save for a first home. For an American saver, the wrapper that makes that work in Britain counts for nothing across the Atlantic.
Relocation packages and the tax nobody put in the budget
Your employer pays for the flights, the movers and the first month's flat. Britain lets some of that go untaxed. America counts every dollar as pay.
Your laptop moved to London. Your employer stayed in America.
The job did not move, only the desk. For tax purposes, the desk is what counts, and it pulls the salary into Britain whatever the payslip says.
RSUs across the Atlantic: when each country takes its share
A single vesting date can be taxed by two countries at once. The split depends on where you worked while the award was being earned, not where you sit on the day it lands.
Stamp duty on a British home, and what it does on your US return
It is often the biggest single cost of buying a home here. The American return will not let you deduct it, but it does not ignore it either.
Your American employer has no UK payroll. Here is who pays the tax.
Gross pay lands in your account every month and nobody has taken any British tax. That is not a windfall. It is a job your employer has quietly passed to you.
Keeping your American house after you move to Britain
Plenty of people move to Britain and keep the house they left behind. Turning it into a let property changes its tax status, its paperwork and the sale that follows.
Form 8621: who files it, when, and for how many funds
One form per fund, attached to your return, with a small-holdings exception most people have never heard of. Here is how the filing side actually works.
Is my fund a PFIC? How to check before you buy
Nothing on a fund factsheet says PFIC. The status comes from American law applied to a foreign company, so you have to work it out yourself.
Junior ISAs when one parent is American
The account belongs to the child, not to you. That single fact decides everything about how the American side treats it.
UK savings interest, the allowances, and your US return
Britain lets most people earn interest untaxed. America taxes the same interest in full, which turns a quiet savings account into a reporting question.
Where Americans in Britain can actually hold investments
The hard part is rarely picking investments. It is finding an account that will take you, and a structure both tax systems treat sensibly.
Form 2555 or Form 1116: choosing your relief from the UK
Both reliefs can zero your US tax on a UK salary. Only one keeps your refundable credits and IRA room - and switching back later is not quick.
National Insurance for Americans working in Britain
It looks like a second income tax, yet it builds a State Pension record and interacts with US social security. Here is how it works for newcomers.
Your P60 and your US return: reading one for the other
The P60 is the most useful document an employed American in Britain receives - and the easiest one to misuse on a US return.
The UK tax year: why 6 April runs your British filings
Britain counts its tax year from 6 April, America from 1 January. That single mismatch touches every figure a cross-border family reports.
Do you need to file a US tax return from abroad?
Owing nothing is not the same as not filing. The duty follows citizenship, the thresholds are lower than people assume, and some forms apply regardless of income.
How to avoid double taxation between the US and UK, mechanism by mechanism
Both countries can tax the same income - yet almost nobody should actually pay twice. Four mechanisms do the work, and the order you apply them matters.
The child tax credit abroad: the refund most expat families miss
Americans abroad often owe no US tax at all - and still qualify for a refundable credit. The catch is that the usual expat election can switch it off.
Form 3520: the report that follows a gift from home
A gift from a British parent is rarely taxable to you. Failing to report it is a different matter, and the penalty runs as a percentage of the gift.
Form 8938 vs the FBAR: two reports, one set of accounts
Same accounts, two different reports, two different agencies. Here is what separates the FATCA form from the FBAR, and why many expats file both.
Married to a Briton: the filing status choice that follows
Marry a Briton and your American return changes shape. The default status carries a $5 filing threshold, and the alternative pulls their income into the US net.
The October 15 deadline: your last stop for this year's US filings
The season ends here: extended returns and the FBAR land on the same day. What must be in, what can wait, and what missing it actually costs.
Register for Self Assessment by 5 October - the American's guide
The 5 October date is the quiet deadline that catches movers. Why Americans in the UK hit it more than anyone, and how to handle it properly.
Streamlined filing cost: the three numbers that decide it
What does a streamlined catch-up actually cost? Three numbers decide it - and the biggest one is often zero for expats. Here is the honest breakdown.
Capital gains tax on shares when you also file in America
Sell shares as an American in Britain and two systems compute the gain: one in sterling, one in dollars. The currency alone can decide whether you profited.
Inheritance tax when one of you is American
Britain taxes the estate, America taxes by citizenship, and the spouse exemption most couples rely on works differently when the survivor is not American.
Payments on account: the UK tax bill that arrives twice
Two advance instalments, a 150% first-year surprise, and a reduction lever most people never pull. The advance-payment system, explained properly.
The statutory residence test in the year you move
Arrival and departure years are where the test bites hardest, and where Americans get it wrong most often. Here is how the three stages actually run.
The exit tax: what renouncing actually triggers
Renouncing does not automatically trigger a charge. Three tests decide it, and the one that catches most people has nothing to do with wealth.
UK rental income and the depreciation trap on your US return
The same tenant and the same rent produce two different profit figures. Depreciation is the widest gap, and its effect follows you all the way to the sale.
The totalization agreement: which country gets your social security
Income tax treaties do nothing for social security. A separate agreement handles it - and it decides whether you pay National Insurance or US payroll taxes.
Delinquent FBAR procedures: three ways back to compliance
Missed FBARs rarely stay missed. Here are the three routes back, what each one costs, and how to pick the right one before the IRS picks for you.
FBAR filing cost: what's free, what isn't, and what drives fees
The government charges nothing to file an FBAR. So where do the fees come from, when is paying someone worth it, and what does skipping it cost?
How HMRC knows about your income - and what to do about it
Wages, bank interest, overseas accounts, platform sales: most of your income reaches HMRC before you ever file. Here is where the data comes from.
The dividend withholding rate under the US-UK treaty, explained
The treaty sets three possible caps on US dividend tax for UK investors: 15%, 5% and zero. Which one applies depends entirely on who owns the shares.
Treaty Article 17: how the US and UK tax your pension income
Periodic pensions, lump sums and social security each follow a different rule in Article 17 - and the saving clause rewrites two of them for US citizens.
Selling a UK home when the IRS is also watching
Private Residence Relief covers the UK side. The US calculates a different gain, in a different currency, with a smaller exclusion.
UK pensions under US rules: where the treaty helps and where it does not
A UK pension is usually fine to hold. The tax-free lump sum is where assumptions get expensive.
Your ISA is tax-free in the UK. The IRS disagrees.
The wrapper does not travel. Worse, most of what sits inside one is a PFIC, and PFIC treatment is punishing by default.
Streamlined filing: getting current, penalty-free on the Foreign Offshore route
The route back for people who did not know they had to file. Narrower than it looks, and worth assessing before you submit anything.
Filing a US return from the UK: what actually changes
The obligation does not go away when you move. What changes is which reliefs you claim and in what order.