US UK accountant for the self-employed for Americans in London

A US UK accountant for the self-employed for Americans in London prepares one integrated package: a UK Self Assessment return with SA103 self-employment pages, a US Form 1040 with Schedule C, a totalisation certificate of coverage that removes US self-employment tax, and a reconciliation between two mismatched tax years.

That last item is the part generalist firms quietly skip. A London-based freelance consultant, screenwriter, architect or independent adviser who holds a US passport is not filing two separate returns that happen to sit in the same folder. They are filing two returns that must agree with each other on profit, on timing, on currency and on which country's social security system has the claim — and that must go on agreeing, year after year, because an inconsistency introduced in one year propagates through foreign tax credit carryovers for a decade. At Jungle Tax we prepare these packages as a single engagement precisely because the reconciliation, not the data entry, is where the money and the risk sit.

What does a US UK accountant for the self-employed actually prepare?

Before discussing rules, it is worth being concrete about the deliverable. A complete annual package for a self-employed American in London contains three distinct work products, and you should expect to see all three.

The UK file

• SA100 — the core Self Assessment return.
• SA103S or SA103F — the self-employment supplementary pages. The full version (SA103F) is required above the VAT registration turnover threshold and wherever the accounts are more complex; the short version suffices for straightforward trades.
• SA106 where there is foreign income, and SA109 where residence or the remittance basis is in point — relevant to Americans who arrived mid-year or retain US-source income.
• A set of accounts to HMRC's standard, the basis-period position, capital allowances computation, and the Class 4 and (where relevant) voluntary Class 2 National Insurance calculation.
• From the 2026/27 tax year onward for many traders, four quarterly updates and a year-end digital submission under Making Tax Digital for Income Tax.

The US file

• Form 1040 with Schedule C (profit or loss from business) and Schedule SE, or a statement removing Schedule SE under the totalisation agreement.
• Form 1116 for the foreign tax credit, and/or Form 2555 for the foreign earned income exclusion — the choice between them is a modelling exercise, not a default.
• Form 4562 where equipment is capitalised, Form 8829 or the simplified method for home office, and Form 8938 where specified foreign financial assets exceed the threshold for an overseas filer.
• FinCEN Form 114 (FBAR) covering the business current account, the personal account, and any account over which the client has signature authority.
• Quarterly estimated tax vouchers where a US liability survives the credits.

The cross-border workpapers

This is the file that distinguishes a specialist. It should contain a calendar-year profit and loss statement rebuilt from the UK books, an expense bridge showing every item allowed in one country and disallowed in the other, a foreign tax credit allocation schedule apportioning UK tax across two US years, a currency translation schedule, and a running carryover memorandum. If your current adviser cannot produce this file, they are producing two returns, not a package.

Sole trader in the UK, sole proprietor in the US: the same trade, two frames

A UK sole trader and a US sole proprietor are the same person for tax purposes, which is convenient, but the two systems measure that person differently. The table below sets out the divergences that actually change the numbers.

Item	UK / HMRC treatment	US / IRS treatment
Tax year	6 April to 5 April	1 January to 31 December
Return form	SA100 plus SA103 self-employment pages	Form 1040 plus Schedule C
Default accounting basis	Cash basis is the default for most unincorporated traders, with an accruals election available	Cash or accrual, elected on the first return and generally sticky thereafter
Filing deadline	31 January following the end of the tax year (online)	15 April, automatically extended to 15 June for those residing abroad, and to 15 October on request
Social contributions	Class 4 National Insurance on profits; Class 2 credited where profits exceed the small profits threshold	Self-employment tax (SECA) at a combined 15.3% on 92.35% of net earnings, above a $400 threshold
Client entertaining	Wholly disallowed	Entertainment disallowed; business meals deductible on a restricted basis
Capital expenditure	Capital allowances, including the annual investment allowance and full expensing regimes	Depreciation, with section 179 expensing and bonus depreciation available
Home working	Simplified flat-rate deduction by hours worked, or an apportionment of actual costs	Simplified square-footage method, or Form 8829 actual costs
Mileage	Approved mileage rates: 45p per mile for the first 10,000 business miles, 25p thereafter	IRS standard mileage rate per business mile, or actual costs
Payments in advance	Payments on account each 31 January and 31 July, each half of the prior year's liability	Quarterly estimated tax instalments in April, June, September and January

How is SA103 profit reconciled to Schedule C profit?

The single most common error we see on inherited files is the assumption that the number at the bottom of the UK accounts can be dropped onto Schedule C after a currency conversion. It cannot, for four reasons.

Accounting basis

Since the reform of the unincorporated regime, the cash basis is the default for most UK sole traders, while a US sole proprietor may be on cash or accrual depending on the election made on the first Schedule C. Where the two differ, invoices raised in March and paid in May land in different years on the two returns. That is not fatal, but it must be tracked deliberately, because the resulting timing difference feeds directly into the foreign tax credit position. Where a freelancer bills large project fees in irregular tranches, aligning the basis on both sides is usually the cleanest planning step available.

Disallowables that differ

Client entertaining is wholly disallowed for UK income tax but a US sole proprietor may deduct qualifying business meals on a restricted basis, so the same restaurant bill produces two different answers. Professional subscriptions, use-of-home, motor costs and pension contributions each follow their own logic on each side. The expense bridge in the cross-border workpapers exists to record these line by line so the two profit figures can be explained to either tax authority on demand.

Capital spend

A London-based freelance photographer who buys a camera body writes it off in the UK through capital allowances and in the US through depreciation, section 179 or bonus depreciation. The two write-off patterns almost never match. Over the asset's life the totals converge; in any single year they diverge, and again the divergence lands on the foreign tax credit.

Currency

Sterling books must be translated for the US return. The IRS accepts a yearly average rate for a trade conducted throughout the year, but individual transactions — the sale of an asset, a large one-off receipt, a tax payment being claimed as a credit — are generally translated at the rate on the day. Foreign tax paid for foreign tax credit purposes is translated at the rate on the date of payment, which is why the date a payment on account left the client's bank account matters more than most people expect.

Which country takes your social security contributions?

This is the highest-value item in the package, and the one most frequently mishandled. The default position under US domestic law is that a US citizen with net earnings from self-employment of $400 or more owes self-employment tax at 15.3% wherever in the world they live. The IRS guidance on self-employment tax for businesses abroad is explicit that the foreign earned income exclusion does not reduce self-employment tax: you take all self-employment income into account even where the income itself has been excluded from income tax.

The relief comes from the US–UK totalisation agreement, not from the income tax treaty. A self-employed person genuinely resident and working in the UK is covered by the UK National Insurance system, and the agreement therefore removes them from the US system. To claim it in practice:

• The certificate of coverage is issued by HMRC, not by the Social Security Administration, because UK residence assigns UK coverage. Americans routinely apply to the wrong authority and lose months.
• A copy of the certificate is attached to the Form 1040, and the self-employment tax line is annotated to indicate exemption with a statement attached.
• The attachment is made each year the exemption is claimed. A certificate obtained once and then filed away in a drawer is the second most common failure we see.
• Class 4 National Insurance is then paid in the UK through Self Assessment. Under current gov.uk National Insurance rates for the self-employed, Class 4 runs at 6% between the lower and upper profits limits and 2% above, with Class 2 treated as paid where profits exceed the small profits threshold.

The arithmetic is stark. On profits of roughly £50,000, US self-employment tax at 15.3% would be several times the UK Class 4 charge on the same profits. A correctly executed certificate of coverage is, for most self-employed Americans in London, the largest single line of value in the annual engagement. It is also worth checking whether voluntary Class 2 contributions should be paid to preserve a UK State Pension record; for an American who may also be building US credits, the interaction of the two records is a planning question in its own right and one we address under cross-border tax planning.

What does Making Tax Digital change for a self-employed American in London?

Making Tax Digital for Income Tax is the most significant UK compliance change to hit sole traders in a generation, and it arrives in phases. Per HMRC's guidance on when you need to use Making Tax Digital for Income Tax, sole traders and landlords are brought in by reference to qualifying income:

• Qualifying income above £50,000 in the 2024/25 tax year — mandated from 6 April 2026.
• Above £30,000 in 2025/26 — mandated from 6 April 2027.
• Above £20,000 in 2026/27 — mandated from 6 April 2028.

Three points matter specifically for the American filer. First, the test is on gross income before expenses, not profit, so a freelancer with high turnover and thin margins can be caught earlier than expected. Second, where a client has both a trade and a rental property, the incomes are aggregated for the threshold test — a common pattern among Americans who let a former US home or a London flat. Third, and most usefully, MTD forces a quarterly digital bookkeeping discipline that makes the US side dramatically easier: once the books are maintained in compliant software in near real time, rebuilding a calendar-year profit and loss statement for Schedule C becomes a query rather than an archaeology project. Clients who resist MTD as an imposition usually change their view after the first year in which the US return is prepared from clean quarterly data.

MTD does not remove the annual return; it changes its shape. Quarterly updates are cumulative summaries, with the tax position finalised once a year. Nor does it change the payment dates. Exemptions exist, including for digital exclusion, and should be considered rather than assumed away.

How are two mismatched tax years actually reconciled?

The UK tax year ends on 5 April and the US year ends on 31 December. There is no election that harmonises them for an individual. The reconciliation is therefore mechanical, and it has two halves.

Rebuilding the income

The Schedule C profit must be computed for the calendar year. Where the books are maintained monthly — which MTD now effectively compels — this is a matter of re-cutting the same ledger between two different dates. Where the books are prepared once a year to 5 April, the preparer is left apportioning, which is defensible only if the trade is genuinely even through the year and indefensible for a consultant whose income is lumpy. This is the single strongest argument for engaging a firm that prepares both returns: the bookkeeping is specified once, in a form that serves both.

Allocating the UK tax

The foreign tax credit on Form 1116 is claimed either on a paid basis or, by election, on an accrued basis. The accrual election is generally irrevocable in its effect on subsequent years, so it is made deliberately or not at all. On a paid basis, the UK tax relevant to a given US calendar year is the tax actually paid in that calendar year — which, given the UK payments-on-account cycle of 31 January and 31 July, means each US year absorbs one balancing payment for the prior UK year and one instalment for the current one. Self-employment profits fall in the general limitation category. Where the credit exceeds the US tax on that category, the excess carries back one year and forward ten. Those carryovers are an asset; they need a schedule that survives a change of adviser.

Exclusion or credit?

For a self-employed American in London the foreign tax credit is usually the stronger choice, because UK effective rates on trading profit typically exceed US rates once National Insurance is set aside, and because the credit generates carryovers while the exclusion does not. The exclusion also cannot shelter self-employment tax, and revoking it once claimed locks the taxpayer out for five years absent consent. That said, the exclusion can win in a low-profit year, in a year of arrival with part-year UK residence, or where the freelancer has significant US-source income against which credits cannot be used. This is a modelling decision, taken annually and documented — not a house style.

The annual compliance calendar

Date	Obligation	Country
31 January	UK Self Assessment filing deadline, balancing payment, and first payment on account	UK
15 April	US Form 1040 due date; first estimated tax instalment; FBAR due date (automatically extended)	US
5 April	UK tax year end — books cut, capital allowances reviewed	UK
15 June	Automatic filing extension for US citizens residing abroad	US
31 July	Second UK payment on account	UK
5 October	Deadline to notify HMRC of chargeability for a first year of self-employment	UK
15 October	Extended US filing deadline; extended FBAR deadline	US
Quarterly	MTD updates for mandated traders; US estimated tax instalments where a liability survives	Both

What else belongs in the package?

A self-employed life generates cross-border reporting well beyond the two trading returns, and the items below are the ones that turn a routine engagement into a disclosure exercise when they are missed.

• The business bank account is a foreign financial account. A UK business current account, an e-money or payment-platform business balance, and a merchant settlement account all count toward the FBAR aggregate. Freelancers who correctly report their personal account frequently forget the trading one.
• US clients issuing Form 1099-NEC. Payments from US-based clients are reported to the IRS with the freelancer's name on them. The income is still UK-taxed where the work is performed in the UK and there is no US permanent establishment, but the return must be prepared so that the reported amounts reconcile to Schedule C, or an IRS notice follows.
• State residency that has not been severed. California, New York, Virginia, New Mexico and South Carolina are notoriously reluctant to release a departing resident. A freelancer who kept a driving licence, a voter registration and a mailing address in a sticky state may have an unfiled state return sitting behind the federal one.
• UK VAT. Registration is turnover-driven and is a UK-only issue, but the place-of-supply rules for services sold to US clients determine whether those fees count toward the threshold at all — a question with real consequences for a consultant whose client base is transatlantic.
• The incorporation trap. Converting the trade into a UK limited company is often the right commercial move and is frequently a poor US one. The company becomes a controlled foreign corporation, bringing Form 5471, the GILTI regime and a materially heavier compliance burden. This decision should never be taken on UK advice alone; we look at it alongside our wider UK tax services and the US consequences together.
• UK pensions and ISAs. A self-employed American paying into a personal pension, or holding a stocks and shares ISA, has treaty and reporting questions attached to both. An ISA is not tax-free to the IRS, and its underlying funds are frequently passive foreign investment companies.

What if the US returns were never filed?

A significant proportion of the self-employed Americans who come to us have filed faultlessly in the UK for years and never filed in the US at all — often because they left the United States before the trade began and were told, incorrectly, that UK tax discharged the obligation. The position is recoverable. Where the failure was non-wilful, the IRS Streamlined Foreign Offshore Procedures allow three years of returns and six years of FBARs to be filed with a non-wilfulness certification and, for a qualifying non-resident, without the offshore penalty. The self-employment tax exemption can be claimed in those catch-up years provided the certificate of coverage position is properly evidenced, which frequently means the catch-up produces no US tax at all.

The mistake to avoid is a "quiet disclosure" — filing back returns without entering a programme — which forfeits penalty protection. Our approach to this work is set out under IRS streamlined filing, and the same cross-border workpapers described above are what make a streamlined submission defensible.

How should you judge a US UK accountant for the self-employed?

Ask four questions before engaging anyone. First, who prepares the UK return and who prepares the US return — and do they speak to each other, or is one outsourced and returned as a PDF? Second, can they show you the expense bridge and the foreign tax credit allocation schedule from an anonymised file? Third, what is their process for the certificate of coverage, and do they re-attach it annually? Fourth, how do they intend to handle MTD quarterly updates alongside the calendar-year rebuild — because a firm that has not thought about this will be re-keying your books twice a year at your expense.

The right answer to all four is a single team holding both qualifications and a single specification for the bookkeeping. That is the model we run for founders, consultants and creative professionals across London, and it is why our US UK tax accountants scope the bookkeeping before they scope the returns. Further reading on adjacent positions is collected in our guides library.

Speak to us before the next cycle begins

If you are self-employed in London and holding a US passport, the difference between a coordinated package and two disconnected returns is measured in thousands of pounds a year and in the strength of your position if either authority ever asks. Whether you are filing correctly and want the position reviewed, or you have a US filing history that stops several years ago, the first step is a confidential conversation about what is actually on file. Contact our cross-border team to arrange a private consultation with a specialist who prepares both sides of the picture.