Introduction: Cross-Border Tax Preparation When You Bank in the City
Cross-border tax preparation for an American working in London is not two tax returns sitting side by side. It is one set of facts, forced through two systems that disagree about almost everything. They disagree about when the year ends. Moreover, they disagree about which country earned your bonus, what your shares are worth, and when your tax was actually paid. Consequently, the errors compound quietly. Most City filers who ask us to review their cross-border tax preparation are not evading anything. Instead, they are losing five and six figures of foreign tax credit through sequencing mistakes nobody warned them about.
Why Cross-Border Tax Preparation Breaks at Banker Income Levels
At £80,000 the two systems roughly cancel out. At £750,000 they do not. Specifically, your income arrives in lumps, your tax is paid on instalment dates that ignore both calendars, and your compensation vests across jurisdictions. Furthermore, the reliefs that protect ordinary expatriates stop working. The foreign earned income exclusion covers a fraction of your salary. Therefore the foreign tax credit carries everything, and its timing rules become the whole game.
What Actually Goes Wrong
Three failures recur in the cross-border tax preparation we inherit. Firstly, filers claim UK tax in the wrong American year and strand the credit. Secondly, they accept a UK planning position that removes British tax without noticing it also removes the credit that was sheltering their US liability. Thirdly, they treat National Insurance as creditable when it is not. Each mistake is invisible on the face of either return. Nevertheless, each is expensive.
Who This Is Written For
This is for American citizens and green card holders working in London banking, private equity, hedge funds and trading. Notably, it applies whether you moved last year or a decade ago. It assumes real money, real complexity, and filings that must survive scrutiny in two countries. Above all, it assumes you would rather understand the mechanics than be told to leave it to somebody.
The Two Calendars That Make Everything Harder
Sound cross-border tax preparation starts with a calendar problem, not a tax problem. Get the calendar wrong and every later number inherits the error.
6 April to 5 April Against 1 January to 31 December
Britain runs its personal tax year from 6 April to 5 April. America runs the calendar year. Consequently, every UK tax year straddles two US tax years, and every US year straddles two UK years. There is no election that aligns them. Therefore cross-border tax preparation must apportion, and apportionment demands payroll records rather than a single P60. Moreover, the HMRC guidance on UK residence and foreign income governs which slice Britain taxes in the first place.
The Deadline Map You Must Hold in Your Head
The dates interlock badly, and cross-border tax preparation has to respect all of them. Britain wants your online return by 31 January following the tax year, with paper returns due 31 October, as HMRC's Self Assessment deadlines set out. America wants your return by 15 April, though citizens abroad receive an automatic extension to 15 June. Additionally, Form 4868 pushes that to 15 October, and a discretionary letter can reach 15 December. Consequently, the sensible order is to prepare Britain first, then America, because the UK liability feeds the American credit.
Making Tax Digital Changes UK Preparation From April 2026
The British side changed materially this year. Making Tax Digital for Income Tax became mandatory from 6 April 2026 for those with qualifying income above £50,000, and HMRC's guidance on using Making Tax Digital sets out the quarterly obligations. Most guidance on cross-border tax preparation still describes this as forthcoming. However, filers who complete the SA109 residence pages are deferred to April 2027, which covers a great many Americans in London. Therefore check your own position rather than assuming the headline applies.
Payments on Account and the Credit Bunching Trap
This section alone justifies professional cross-border tax preparation. Careless filing quietly loses money here every year.
How HMRC's Two Instalments Distort Your American Credit
Where your Self Assessment liability exceeds £1,000, HMRC demands payments on account in two instalments. They fall due on 31 January and 31 July. Each is half of the previous year's liability. Consequently, a single American calendar year can contain a balancing payment for one UK year plus two instalments for the next. In a rising bonus year, close to two years of British tax lands inside twelve American months.
Why That Wrecks Form 1116 on the Cash Basis
By default, Form 1116 claims foreign tax in the year you pay it. Therefore the bunched year claims an enormous credit against income that partly belongs to the previous year. Meanwhile the earlier year shows US tax with too little credit to cover it. The excess carries forward for ten years under the IRS foreign tax credit rules. Nevertheless, carryforwards need future foreign income in the same basket to absorb them. Many bankers never generate it, so cross-border tax preparation that ignores timing lets the credit simply expire.
The Section 905(a) Accrual Election
The fix is to elect the accrual basis under section 905(a). Thereafter you claim UK tax in the American year the income arose, not the year the cheque cleared. Consequently, the credit lines up with the income it relates to, and the bunching disappears. Importantly, the election is irrevocable. Once made, you accrue forever, and you must amend when HMRC later changes your liability. Therefore we model several years before recommending it, and we rarely regret making it for a banker with a rising bonus.
Why the FIG Regime Is Worth Less to an American
Cross-border tax preparation changed again when Britain replaced the non-domicile rules on 6 April 2025. Most cross-border articles have not caught up, and several still explain the remittance basis as though it exists.
The Four-Year Exemption That Does Not Reach Your US Return
The foreign income and gains regime exempts qualifying new arrivals from UK tax on foreign income and gains for four years. It applies after ten tax years of non-residence. For a French or Australian arrival, that genuinely means four years tax free. For an American, it does not. Specifically, the United States still taxes the same income by citizenship, at rates reaching 37 per cent under the 2026 federal brackets. Britain steps back, and America simply fills the space, which cross-border tax preparation must anticipate.
The Allowances You Surrender to Claim It
Claiming the regime costs you the UK personal allowance and the capital gains annual exempt amount. At £750,000 the personal allowance has already tapered away, so a banker surrenders little. However, an American with modest foreign income can pay more overall by claiming than by not claiming. Therefore the election deserves arithmetic within your cross-border tax preparation, not enthusiasm.
What This Means for Your Credit Position
There is a subtler cost. During the exempt years you accrue no British tax on that income. Consequently, you build no excess credits to shelter other passive income, and you arrive at year five with nothing banked. Meanwhile the American liability has run at full rate throughout. We therefore model the whole four years and the cliff beyond, alongside our cross-border planning team.
Bonus, Deferred Compensation and Share Awards
Compensation is where cross-border tax preparation becomes genuinely technical, and where most reviews find money. Banking pay rarely belongs to one year or one country.
Sourcing a Bonus Earned Across Two Countries
A bonus compensates a performance period, not a payment date. Therefore a bonus paid in March 2027 for calendar 2026 may be partly US-source if you spent part of that period working in New York. Consequently, sourcing follows workdays, and workday records decide how much credit you may claim. Additionally, the source rules determine the Form 1116 basket. Filers who source by payment date routinely overstate their foreign income and lose credit on audit.
Deferred Cash and the Year Britain Taxes It
Deferred awards create the sharpest mismatches. Britain generally taxes deferred cash when it is paid, while America may tax under its own timing rules for non-qualified deferred compensation. Consequently, the two countries can tax the same award in different years. Furthermore, a credit claimed in the wrong year is simply lost. Therefore sound cross-border tax preparation maps every tranche to both calendars before either return is drafted.
Employment Related Securities on Both Returns
Share awards carry a further layer. Britain taxes vesting under the employment related securities rules, and the section 431 election must be signed within fourteen days of acquisition. America runs a separate clock, since a section 83(b) election allows thirty days. Consequently, the deadlines differ and neither country reminds you. Missing either one is permanent.
FEIE or Foreign Tax Credit at City Income Levels
Ordinary expatriate advice recommends the exclusion. That advice does not travel to the City. At banker income that advice is usually wrong, and occasionally expensive.
Why $132,900 Barely Registers
The foreign earned income exclusion rises to $132,900 for 2026, claimed on Form 2555. Against a £750,000 package that covers a small fraction. Meanwhile the excluded slice is the cheapest, lowest-rate portion of your income. Therefore the exclusion removes very little American tax while creating a real cost elsewhere.
The Credit You Forfeit by Excluding
Section 911(d)(6) denies any foreign tax credit for tax paid on excluded income. Consequently, claiming the exclusion also discards the British tax attributable to that slice. For someone paying 45 per cent in Britain and 37 per cent in America, that discarded credit is worth more than the exclusion saves. Therefore the credit alone almost always wins at this level, and IRS Publication 54 sets out both mechanisms.
National Insurance Earns You Nothing
National Insurance is not an income tax, so it is not creditable on Form 1116. Consequently, your employee contributions reduce your cash without reducing your American liability. Furthermore, the US-UK totalisation agreement governs which country's system you pay into. Many City filers wrongly include National Insurance in their foreign tax total, which inflates the credit and invites correction.
The Reporting Layers Sitting Beneath the Two Returns
Filing correctly is not the same as reporting correctly, and cross-border tax preparation covers both. Penalties here attach to forms, not to tax.
FBAR, Form 8938 and What Counts
Your UK current account, savings, brokerage and any account you merely sign on belong on the FBAR once aggregate balances pass $10,000. Separately, Form 8938 reports specified foreign financial assets at higher thresholds. Additionally, translation must use a consistent published rate, and Bank of England data often supports it, and the IRS currency guidance explains acceptable sources. We handle this through our FBAR and FATCA reporting service.
Correcting Years Already Filed Wrongly
Errors of this kind are common in unspecialised cross-border tax preparation, and they are correctable. Where the failure was non-wilful, the IRS Streamlined Filing Compliance Procedures allow three years of returns and six years of FBARs to be corrected without penalty for qualifying taxpayers abroad. Moreover, an amended return claiming foreign tax credits enjoys a ten-year window rather than the usual three. Therefore old credit mistakes are often still recoverable through our IRS Streamlined Filing service.
A Worked Case Study: A £750,000 City Package
Consider a client we will call Nina, an American managing director in London equities. They moved from New York in September 2025 after fourteen years in America.
The British Position for 2026/27
Nina's package comprises £250,000 of salary, a £400,000 cash bonus paid in March 2027, and £100,000 of shares vesting in the same year. Their personal allowance tapers away entirely. Consequently, UK income tax runs to roughly £323,700, with employee National Insurance of about £14,700. Their British return is straightforward. Their American one is not, and this is exactly where cross-border tax preparation earns its fee.
Where the Credit Went Missing
In calendar 2027 Nina actually pays three British amounts outside payroll. Specifically, a balancing payment of £48,000 for 2025/26 falls due on 31 January 2027, alongside a first payment on account of £62,000. A second instalment of £62,000 follows on 31 July. Therefore £172,000 of British tax is paid inside one American year, on top of PAYE. On the cash basis their 2027 Form 1116 claims all of it, while the income it relates to sits partly in 2026. Roughly $54,000 of credit becomes an excess carryforward with no future foreign income to absorb it.
What Coordination Actually Saved
Electing accrual under section 905(a) moved each year's British tax back to the year the income arose. Consequently, the 2026 return absorbed its own credit and the 2027 excess largely disappeared. Additionally, Nina had been advised to claim the four-year regime on $180,000 of American portfolio income. Britain would have charged nothing, yet America would still have taken about $42,800, so the headline benefit was largely illusory for a US citizen. Above all, coordinated cross-border tax preparation recovered far more than the fee for preparing both returns.
How TaxYork Can Help With Cross-Border Tax Preparation
TaxYork prepares American and British returns for high-net-worth individuals, investors and company owners. Specifically, we build one dataset and drive both returns from it, which removes the mismatches described above. Furthermore, we map every bonus and share tranche to both calendars before drafting. We model the section 905(a) election across several years rather than guessing. Additionally, we test the four-year regime properly, including its cost at year five. Where earlier years are wrong, we correct them and reclaim credits still inside the ten-year window. Our team works exclusively on US-UK matters, and City compensation is our daily work. We also coordinate treaty positions through our tax treaty optimisation service.
Conclusion
Cross-border tax preparation for a London banker is a sequencing discipline before it is a filing exercise. Britain and America disagree about the year, the source and the timing, and every disagreement has a price. Consequently, the foreign tax credit is where value is won or lost, and payments on account are where it most often leaks. Meanwhile the four-year regime that thrills your non-American colleagues delivers you far less than advertised. Nevertheless, none of this is unmanageable. Map the calendars, source the compensation by workdays, model the accrual election, and keep National Insurance out of your credit. Disciplined cross-border tax preparation does all four as a matter of routine. Ultimately, coordinated preparation costs less than the credits careless preparation wastes.
Contact Us
To have both returns prepared from one coordinated dataset, book a consultation with our cross-border team. Email hello@taxyork.com or telephone 020 3488 8606. We will review your last three years and tell you what your current approach is costing.
Disclaimer
This article provides general information on cross-border tax preparation for Americans working in the United Kingdom. It does not constitute tax advice for any particular person or transaction. Tax law changes frequently. The figures cited reflect the 2026/27 British tax year and the 2026 American tax year, and the case study is illustrative. You should obtain professional advice tailored to your circumstances before acting. TaxYork accepts no liability for any action taken in reliance on this material. Further guidance is published by HM Revenue and Customs and on UK income tax rates.