US UK Tax Returns Preparation for City Finance Executives

US UK tax returns preparation for an American working in the City means producing two returns on two different tax years: the UK Self Assessment for the year to 5 April, due online by 31 January, and the US Form 1040 for the calendar year, due 15 April with an automatic extension to 15 June abroad and an optional extension to 15 October.

For a senior finance professional, the difficulty is rarely whether to file. It is sequencing: bonuses, deferred awards and restricted stock units hit both systems at different moments, the foreign tax credit has to bridge two tax years that overlap by only nine months, and payment deadlines on each side can catch you out even when the final liability is modest. This guide sets out how disciplined US UK Tax returns preparation works year after year, what each return needs, the order in which they should be prepared, and what a combined engagement costs. It is written from the compliance chair: what must be reported and when, not how to restructure your affairs.

Why does an American in the City file two tax returns every year?

The United States taxes its citizens and green card holders on worldwide income wherever they live. The United Kingdom taxes its residents on worldwide income too, and since 6 April 2025 the old remittance basis has been replaced by a residence-based regime with a four-year relief for foreign income and gains available only to those arriving after ten consecutive years of non-residence. A US citizen who has lived in London for several years is therefore taxed in full by both countries, and the US-UK income tax treaty's saving clause preserves the US right to tax its own citizens as if the treaty did not exist, subject to specific exceptions.

Double taxation is avoided mainly through credits, not exemption. In broad terms, the UK taxes UK-source employment income first, and the US gives a foreign tax credit for UK tax paid. Because UK marginal rates on high earnings generally exceed US federal rates, a City professional whose income is mostly UK-source salary and bonus often ends with little or no residual US federal tax. Little or no tax is not the same as no filing, however, and the information returns that sit alongside the 1040 carry penalties that are entirely independent of tax owed.

At Jungle Tax, we see the same pattern repeatedly: the arithmetic of the credit usually works, and the problems arise from timing, sourcing and data gaps. Those are what this guide addresses.

The two tax years, side by side

Everything in a dual-filing engagement flows from one structural fact: the UK tax year runs from 6 April to 5 April, while the US tax year is the calendar year. Your 2026 US return therefore draws on two UK tax years: roughly three months of 2025/26 (1 January to 5 April 2026) and nine months of 2026/27 (6 April to 31 December 2026).

For an individual with straightforward PAYE salary, the mismatch is mechanical. For someone with a bonus paid in March, deferred cash vesting in multiple tranches, RSUs vesting quarterly and a taxable investment portfolio, it is the single biggest source of preparation error.

In what order should the UK and US returns be prepared?

The common shorthand is "file the UK return first, because the UK tax figure drives the US credit". That is directionally right but incomplete for a City professional, because the US return for calendar year 2026 needs UK tax figures from two UK years, one of which will not close until 5 April 2027. The sequencing that works in practice looks like this:

1. April to June: the UK year to 5 April has just closed. Gather the P60, any P11D, payslips for the final months, and broker statements. Prepare the UK return early, ideally between May and September, not in January. This gives a final UK liability for that UK year.
2. Same window: use that final UK liability, together with the year-to-date payroll position for the new UK year, to prepare the US return for the previous calendar year. Most London-based clients use the automatic 15 June date or extend to 15 October so that the UK figures are firm.
3. By 15 April: regardless of extension, estimate the residual US liability (often nil, sometimes material where there is significant US-source or investment income) and pay it. Interest runs from 15 April on any unpaid balance, and the June extension does not change that.
4. By 15 October: file the extended 1040 and the FBAR, which has an automatic extension to the same date.
5. By 31 January: file the UK return, if not already filed, and settle the balancing payment plus the first payment on account for the current year.

Preparing the UK return early is the single most valuable habit. It turns the UK liability from an estimate into a fact before the US return is finalised, it reduces the chance of an amended 1040 later, and it surfaces problems with PAYE coding on share awards while there is still time to correct them.

What if the US return has to be finalised before the UK figures are known?

It happens, typically when the UK year to 5 April of the following year is still open. The usual approach is to use the payroll tax actually deducted under PAYE for the relevant months, which for most employees is very close to the final liability, and to amend the 1040 if the final UK figure differs materially. On the UK side, where you claim credit for US tax that is not yet final, HMRC practice allows an estimated figure that is then corrected once the US position is settled.

How the foreign tax credit bridges two tax years

The US foreign tax credit is claimed on Form 1116. It is limited, by category of income, to the US tax that would otherwise be payable on foreign-source income in that category. Employment income falls in the general category; interest, dividends and most gains fall in the passive category, subject to the high-tax rules. Unused credits can generally be carried back one year and forward ten years, which matters a great deal for City earners: in high-bonus years UK tax often exceeds the US limit and the excess becomes a carryforward that can absorb US tax in a later year.

Cash versus accrual basis

A taxpayer can claim foreign taxes in the year they are paid (the cash basis) or in the year they accrue (the accrual basis). Once the accrual election is made it binds future years. The choice matters for UK employees because PAYE is deducted month by month while the final UK liability for a tax year is fixed only after 5 April. Many practitioners match UK tax to the calendar year by taking the PAYE actually deducted in January to December and adjusting for any Self Assessment balancing payment relating to the same income. Whichever method is used, it must be applied consistently and the carryforward schedule must be maintained year on year. Inconsistency between years is one of the most common reasons we find stranded or duplicated credits when reviewing returns prepared elsewhere.

Sourcing is as important as timing

The credit only works against foreign-source income. Salary for work performed in London is UK-source. But City professionals travel: days spent working in New York, at a US client or at a US offsite produce US-source income on which the US has the primary claim and the UK credit cannot shelter the US tax. On the UK side, the treaty and UK rules then govern whether the UK gives relief for US tax on those days. Accurate workday records are therefore not a formality; they directly determine how much of each bonus and each vest is US-source.

Bonus, deferred awards and RSUs: how each side reports them

This is where generalist guidance falls silent and where most of the preparation effort sits for an executive return.

Cash bonus

In the UK, a bonus is employment income of the tax year in which it is received or, if earlier, in which you become entitled to it, and it is taxed under PAYE through payroll. In the US, a cash-basis individual reports it in the calendar year it is paid. A bonus paid in March 2026 therefore sits in the UK 2025/26 year and in the US 2026 calendar year, while a bonus paid in May 2026 sits in UK 2026/27 and still in US 2026. The bonus is generally sourced by reference to where the work was performed during the period to which it relates, which can straddle years and countries.

Deferred cash and deferred share awards

Deferred bonuses under regulatory remuneration rules typically vest over several years and may be subject to malus and clawback. They are generally taxed when they vest or are paid, not when they are awarded, on both sides. The preparation challenge is threefold: identifying which tranches vested in which tax year on each side, sourcing each tranche over its own service period, and recording any clawback correctly if it later occurs.

Restricted stock units

RSUs are generally taxed as employment income at vesting on the market value of the shares delivered. In the UK, where the shares are readily convertible assets, the employer operates PAYE and National Insurance at vest, often by selling shares to cover. In the US, the same value is wage income in the year of vesting. The US sources RSU income by reference to the days worked in each country between grant and vest, so an award granted while you were in New York and vesting after you moved to London is partly US-source and partly UK-source. The UK applies its own time-apportionment rules for internationally mobile employees. When the shares are later sold, both countries tax the gain over the vest-date value, but with different rates, allowances, matching rules and currency conventions, so the sterling gain and the dollar gain can differ materially, and occasionally one will be a gain while the other is a loss.

Reporting UK investment income on both returns

The investment side of a City professional's return is where US and UK rules diverge most sharply, and where a well-run UK portfolio can create disproportionate US compliance work.

• ISAs: tax-free in the UK, fully taxable in the US. Interest, dividends and gains inside an ISA must be reported on the 1040, and the account is reportable on the FBAR and, where thresholds are met, Form 8938.
• UK funds: OEICs, authorised unit funds and many UK-domiciled ETFs are generally passive foreign investment companies for US purposes. Each requires Form 8621 analysis, and the default US regime is punitive. A portfolio of a dozen UK funds can generate more US preparation hours than the entire employment section.
• Dividends and interest: taxed on both sides, with UK tax creditable in the US passive category. UK allowances (the dividend allowance and the personal savings allowance, which is nil for additional-rate taxpayers) have no US equivalent.
• Capital gains: both countries tax gains on UK-resident US citizens. Different holding-period rules, rates and currency treatment mean the gains rarely match. A gain on a sterling asset can be a dollar gain, a dollar loss or a pure exchange gain.
• US brokerage and dividend income: US-source income received while UK resident is taxable in the UK, with treaty relief for the US tax, and the treaty's re-sourcing rules interact with the US credit. These calculations should be prepared deliberately, not left to default software settings.
• UK workplace pensions: the treaty contains specific provisions on contributions to and growth within UK schemes. Correct treatment often requires a treaty-based disclosure and must be applied consistently each year.

If any of these items has not been reported in past years, the remedy is a compliance catch-up rather than a quiet correction in the current year. Our IRS streamlined filing team handles that process for non-willful filers.

FBAR and Form 8938 alongside the 1040

Two separate foreign asset disclosures sit alongside the US return each year:

• The FBAR (FinCEN Form 114), filed electronically and separately from the 1040, is required when the aggregate maximum value of non-US financial accounts exceeds $10,000 at any point in the calendar year. It is due 15 April with an automatic extension to 15 October. UK current accounts, savings accounts, ISAs, brokerage accounts and many pension arrangements are within scope, as are accounts over which you have signature authority, which can include employer accounts for senior finance staff.
• Form 8938 is attached to the 1040. For taxpayers living abroad, the thresholds are $200,000 at year-end or $300,000 at any time during the year for single filers, and $400,000 or $600,000 for married couples filing jointly. Most City professionals with substantial UK savings, ISAs and pensions exceed them.

The two forms overlap but are not identical, and filing one does not satisfy the other. Penalties for non-filing apply regardless of whether any tax is due. If you want to understand potential exposure on historic gaps, our FBAR penalty calculator gives an indicative view before you speak to us.

Payments on account and US estimated payments

Cash-flow surprises are common in the first and second years of dual filing, and they arise from two parallel prepayment systems.

UK payments on account

Where your Self Assessment liability for a year exceeds £1,000 and less than 80% of your total liability was collected at source, HMRC requires payments on account towards the following year, each equal to half of the previous year's Self Assessment liability, due on 31 January and 31 July. A large RSU vest that is under-taxed through PAYE, a significant investment gain, or untaxed US income can push you into payments on account for the first time, so the January payment can be one and a half times the prior year's Self Assessment bill. A claim to reduce payments on account is available where income is expected to fall, but over-reducing triggers interest.

US estimated tax

The US collects tax during the year through quarterly estimates on Form 1040-ES, normally due 15 April, 15 June, 15 September and 15 January. Because UK payroll does not withhold US tax, a City professional with residual US liability, typically on US-source workdays, US investment income or tax the foreign tax credit cannot reach, should consider estimates to avoid the underpayment penalty. The safe-harbour rules for higher earners refer to a percentage of the prior year's liability, and a well-prepared prior-year return makes those calculations straightforward.

A data-gathering calendar for the dual filer

The most efficient engagements run to a fixed annual rhythm rather than a January scramble. A typical calendar for a London-based American finance professional:

The core document set each year includes the P60 and P11D, payslips showing bonus and share-award payroll entries, equity plan statements with grant, vest and sale data, workday or travel records, broker statements and consolidated tax certificates from UK and US accounts, pension statements, highest-balance figures for every non-US account, the prior year's foreign tax credit carryforward schedule, and both prior-year returns.

What does combined US and UK return preparation cost?

Fees for a coordinated engagement are driven far more by complexity than by income level. Published pricing for straightforward expat returns starts in the hundreds of pounds per return, but that pricing assumes salary, a bank account and little else. For a City professional, the following drivers determine where an engagement lands:

• Equity compensation: the number of plans, vesting events and sales, and whether awards straddle a move between countries and require day-count sourcing.
• UK fund holdings: each passive foreign investment company requires its own annual analysis; a large fund portfolio is often the largest single fee driver.
• Foreign tax credit history: whether carryforwards have been tracked consistently or need to be rebuilt from prior returns.
• Travel and workdays: material US workdays require apportionment across both returns.
• Number of accounts: FBAR and Form 8938 workload scales with the number of accounts and the quality of statements.
• Joint filing choices: a non-US spouse raises a choice of filing status that must be modelled before filing.
• Remediation: any prior-year gaps add catch-up work, which is quoted separately.

As an indicative guide only, a combined US and UK engagement for a senior City professional with equity awards and a moderate investment portfolio commonly sits in the low-to-mid thousands of pounds a year, rising into five figures where there are multiple equity plans, extensive UK fund holdings or remediation. The real economic test is whether the engagement prevents double taxation, preserves carryforwards and avoids penalties; for this client profile, the tax at stake each year dwarfs the fee. Our high-net-worth practice quotes fixed fees after a scoping review of the prior year's returns.

Common errors we correct on City professionals' returns

• Claiming UK tax as a credit against US-source workday income, overstating the credit.
• Reporting RSU income in the wrong UK year because the vest date and payroll date differ.
• Omitting ISA income from the 1040 because it is tax-free in the UK.
• Treating UK funds as ordinary shares and ignoring Form 8621 obligations.
• Switching between cash and accrual credit methods year to year, stranding credits.
• Leaving out accounts with signature authority from the FBAR.
• Missing the UK 5 October registration deadline in the first year a vest is under-taxed.
• Using different exchange rate conventions on each side without documenting them.

When separate advisers become a liability

Many Americans in London engage a UK accountant and a separate US preparer. Each may be competent, yet the returns can still fail to reconcile: the US preparer works from estimated UK tax, the UK accountant does not see the US sourcing, and nobody owns the foreign tax credit carryforward schedule. Coordinated preparation by one team that prepares US returns and UK returns in the same workflow removes those hand-offs, which is where most errors originate. Timing guidance on UK deadlines is available on GOV.UK, but for an executive return the question is rarely the deadline itself; it is having both sets of figures settled in time to meet it.

Arrange a confidential review

If you are an American working in the City and want your US and UK returns prepared as one coordinated engagement, with consistent foreign tax credit tracking, accurate equity sourcing and every disclosure filed on time, contact our cross-border team for a confidential consultation. We will review your most recent returns, identify any gaps, and set out a fixed-fee preparation plan for the year ahead.