Tax Preparation Services US and UK: What's Included and What Costs Extra

Tax preparation services for the US and UK usually include what is needed every year: the US federal Form 1040, the UK Self Assessment return with its supplementary pages, the FBAR and the foreign tax credit that links the two. What is included beyond that, such as PFIC forms, state returns, amendments or authority letters, depends on the engagement letter. This guide goes through the scope line by line, so you can see what a fee should cover, what is normally extra and why.

Our plain-English guide to US/UK tax services maps services to situations, and our walk-through of the US/UK cross border tax preparation process covers the stages from engagement to payment. This article sits between the two. It is about the contents of the box: the individual forms, the events that change the price, and how to read the letter that fixes the scope before any work begins.

What is included in tax preparation services for the US and UK?

A core cross-border engagement for an individual normally covers one US federal return, one UK return and the reporting and relief that connect them. In practice that is five things, and a well-drafted engagement letter will name each of them.

1. The US federal return, Form 1040. US citizens and green card holders report worldwide income every year wherever they live. The preparer converts UK salary, interest, dividends and gains into dollars and places them on the right schedules.
2. US double-tax relief. For most UK residents this is the foreign tax credit on Form 1116, which credits UK tax paid against the US tax on the same income. Some people instead, or as well, claim the foreign earned income exclusion on Form 2555. The IRS is clear that you cannot take a foreign tax credit on income you have excluded, so choosing between them is part of the preparation, not an add-on.
3. The FBAR, FinCEN Form 114. Required when your non-US accounts together exceed $10,000 at any time in the calendar year. It is filed with FinCEN, not with the tax return.
4. The UK Self Assessment return, SA100. The main return plus the supplementary pages your income needs, listed in the table below.
5. UK double-tax relief and treaty positions. Where the US has taxed income first, for example US-source dividends or rent from a US property, the UK return claims Foreign Tax Credit Relief on the foreign pages.

Our tax preparation services US and UK are built around that core, with the extras below quoted once we know the facts. US/UK Cross Border Tax — US CPAs and UK tax advisers working as one team; London, Manchester, New York, San Francisco — prepares both sides together, so the relief claimed on one return matches the tax reported on the other.

The UK side: which Self Assessment pages are in scope?

The UK return is modular. The SA100 is the core, and HMRC publishes a separate set of supplementary pages for each type of income. Scope creep on the UK side usually means a new page has become necessary.

Page	What it covers	Typical position in a fee
SA100	Main return: UK interest, dividends, pension contributions, Gift Aid	Core
SA102	Employment and directorships	Core for most employees
SA103S / SA103F	Self-employment (short and full versions)	Often priced by complexity
SA104S / SA104F	Partnership share	Often priced by complexity
SA105	UK property income	Frequently an extra per property or portfolio
SA106	Foreign income and gains, including US income and Foreign Tax Credit Relief	Core for cross-border clients
SA108	Capital gains	Often priced by number of disposals
SA109	Residence: non-UK residents and dual residents	Extra in an arrival, departure or split year

For the 2025/26 tax year, GOV.UK sets the Self Assessment deadlines at 31 October 2026 for paper returns and 31 January 2027 for online returns, with the tax due by 31 January 2027. An engagement letter should say which deadline the firm is working to and what it needs from you, and by when, to meet it. Our UK Self Assessment service covers the UK side in more detail.

The US side: what sits outside a basic Form 1040?

On the US side, the form list is where fees diverge. A Form 1040 with UK salary, a foreign tax credit and an FBAR is a known quantity. The following forms each bring their own work and are the usual source of additional charges.

Form 8938 (FATCA)

Form 8938 reports specified foreign financial assets and is attached to the tax return. According to the IRS comparison of Form 8938 and FBAR requirements, for the 2025 tax year a taxpayer living abroad who is unmarried files when those assets exceed $200,000 on the last day of the year or $300,000 at any time; for married couples filing jointly the figures are $400,000 and $600,000. Many firms include Form 8938 with the FBAR because the account data overlaps, but others price it separately. Our guide to the FBAR versus Form 8938 sets out the differences.

Form 8621 (PFICs)

A Form 8621 is filed by a US person who holds shares in a passive foreign investment company and meets the filing conditions, which include receiving distributions, selling shares, making elections or the annual reporting requirement. UK unit trusts, OEICs and many funds inside an ISA or general investment account fall into this category. The work is per fund, which is why it is almost always priced per form. See ISAs and the PFIC problem and our PFIC reporting service.

Other information returns

• Form 3520, the annual return for transactions with foreign trusts and receipt of certain foreign gifts, for example a large gift or inheritance from a UK parent.
• Form 5471, the information return for US persons who are officers, directors or shareholders of certain foreign corporations, which catches many Americans who run a UK limited company.
• Form 8833, the treaty-based return position disclosure, needed when a return relies on the US/UK treaty to override the Internal Revenue Code.
• State returns. Depending on your last state of residence and any US-source income, a state return may be required. These are normally quoted individually.

What typically counts as extra?

Items outside the core are usually extra because the work is driven by events rather than by the annual cycle. The table below is a reading guide, not a price list: firms differ, and the only reliable answer is the one in your engagement letter.

Item	Why it is often scoped separately
Form 8621 for each PFIC	Calculation per fund; volume varies widely between clients
US state returns	Different rules and forms in each state
Forms 3520 and 5471	Specialist information returns with their own schedules
Amended returns (Form 1040-X, or a UK amendment)	Reopening a filed year, often with someone else's workpapers
Streamlined catch-up filings	Several years of returns and FBARs in one package
IRS or HMRC correspondence beyond simple queries	Open-ended; depends on what the authority asks
Property disposals and share scheme events	Basis, currency and timing calculations in both countries
Arrival, departure or split years	Residence tests, SA109 and part-year US positions
Tax planning and projections	Advice work, separate from preparing what already happened

Amendments

If a prior return needs correcting, the US uses Form 1040-X and the UK allows amendments to a Self Assessment return within set time limits. An amendment is a separate job, because the preparer has to reconstruct the original position before changing it, and often did not prepare the original.

Streamlined filings

The IRS Streamlined Foreign Offshore Procedures require eligible non-willful filers living abroad to file returns for the most recent three years for which the due date has passed, FBARs for the most recent six years, and a signed Form 14653 certification. Where a return was previously filed, it is amended on Form 1040-X. That is a project with its own quote. Our Streamlined procedures guide explains who qualifies.

IRS and HMRC correspondence

Most letters follow a processing mismatch and are resolved quickly. Enquiries, examinations and penalty appeals are different. Representation before the IRS requires Form 2848, and HMRC deals with an agent once the client has authorised them, for example through the 64-8 authorisation. If a letter arrives, our IRS representation service picks it up.

How do you read an engagement letter for US and UK returns?

Read the engagement letter as a list of named deliverables, exclusions and triggers. If a form is not named, assume it is not included until the firm confirms otherwise in writing. Five clauses carry most of the weight.

1. The deliverables clause. Look for form numbers, not descriptions. "US and UK tax returns" is vague; "Form 1040 with Form 1116, FinCEN Form 114, SA100 with SA102 and SA106" is a scope.
2. The exclusions clause. A good letter lists what is out: PFIC forms, state returns, prior years, planning. An empty exclusions clause is not generosity; it is ambiguity.
3. The additional fees clause. What triggers a revised quote, and does the firm tell you before doing the work or after? Common triggers are a new account, a property, a fund, a gift or a change of residence.
4. The client responsibilities clause. Who compiles the list of accounts and maximum balances for the FBAR, and what happens if documents arrive late. Missed information deadlines are where filing deadlines are lost.
5. The correspondence and representation clause. Whether replies to IRS and HMRC letters on the prepared returns are included, and where the line falls between a query and an enquiry.

Also check the timetable. US citizens and resident aliens living abroad who meet the IRS conditions receive an automatic two-month extension of the filing date to 15 June, but the IRS charges interest on any tax not paid by the regular April date. A letter that assumes an extension should say so, and say whether preparing an extension request is included. If you are comparing letters from several firms, our guide on comparing cross-border tax providers fairly gives a scorecard for putting the same scope to each firm.

Illustrative example: an American teacher in Manchester has UK salary, a UK current account and a stocks and shares ISA holding three UK funds. The core engagement covers her Form 1040 with Form 1116, the FBAR, and her SA100 with the employment pages. The three ISA funds are likely PFICs, so the preparer lists three Form 8621s as an additional item. Mid-year she inherits money from her British grandmother; that may bring a Form 3520 into play if the amount crosses the IRS threshold, and the engagement letter's additional fees clause is what tells her how that will be handled. This is illustrative only; the right scope depends on the individual's facts.

What do people get wrong about what is included?

• Assuming the FBAR is part of the return. It is a separate filing to FinCEN, and it is sometimes left out of a quote without anyone noticing.
• Treating an ISA as invisible to the US. The UK wrapper has no status on a US return, and the funds inside may need Form 8621s.
• Not mentioning events at the quote stage. A property sale, share vesting, a gift from abroad or a move are all scope changes. Raising them at the start lets the firm price them; raising them in January creates a dispute.
• Comparing headline fees instead of form lists. Two quotes are only comparable when they cover the same named forms.
• Assuming a letter from HMRC or the IRS is covered. Some firms include replies on returns they prepared; many charge for enquiries. The letter decides.
• Forgetting the UK side of US income. Rent from a US property or dividends from US shares belong on the UK return too, usually on the SA105 or SA106, with relief for US tax.

Before you sign: a short checklist

Send the firm a single list before it quotes: your citizenship and residence, every account in each country with its approximate maximum balance, every investment fund, any property, any business you own, any gift or inheritance from abroad, and any year you did not file. Ask for a quote that names the forms, lists the exclusions and states the triggers for extra work. That is the same information the preparer will need anyway, and giving it up front turns most would-be surprises into agreed line items.

If you are an American in Britain, our page for Americans living in the UK sets out the filings that usually apply. When you are ready for a scoped quote that covers both returns, contact us with the list above and we will come back with the forms, the exclusions and the timetable in writing.