The SA100 (opens the official HMRC page in a new tab) is the main UK Self Assessment return: personal details, UK interest and dividends, UK pensions, reliefs and a page of questions that decides what else goes in. A US citizen living in the UK usually adds supplementary pages to it. SA102 covers a job, SA103 self-employment, SA105 UK rent, SA106 anything paid from the United States, SA108 gains, and SA109 residence claims.
This post is for US citizens who already know they file in the UK and want to see what the return holds. It maps US-sourced income to the right page and explains why the UK figures come first. Whether you must file at all is covered in our post on Self Assessment for Americans on PAYE, and the wider annual cycle in our guide to US and UK tax returns for Americans in the UK.
What does the SA100 contain for a US citizen in the UK
The SA100 is the core form. It records UK savings and dividend income, UK pensions and state benefits, pension contributions and Gift Aid, and a page of yes or no questions that decides which supplementary pages you attach. For most Americans in Britain, the US items sit on those added pages rather than on the SA100 itself.
The question page sets the shape of the return. HMRC's notes say a Yes answer there commits you to sending the matching supplementary pages, and a return with a ticked box but missing pages is treated as incomplete and sent back. A paper booklet posted by HMRC reflects what it already knows about you, so checking that every required page is present falls to the filer.
The main form still holds UK bank interest, UK dividends, pension contributions claiming relief and Gift Aid. Its free-text box for other information near the end is where HMRC asks for details of a foreign pension that a treaty takes out of UK tax. Our SA100 form guide covers the main form, and the pages that can sit behind it are these:
- SA100: the main return, with UK interest, UK dividends, UK pensions and reliefs
- SA102 Employment: one page per job or directorship, including work for a US employer with no UK payroll
- SA103 Self-employment: short or full pages, one set per business
- SA105 UK property: rent from land or buildings in the UK
- SA106 Foreign: US interest, dividends, rent, pensions and Social Security, plus the credit for US tax
- SA108 Capital gains and SA109 Residence: disposals anywhere in the world, and claims that turn on residence
Which supplementary pages does an American in the UK need
Work from the income, not the passport. US citizenship adds nothing to the UK return on its own; UK residence brings worldwide income into charge, and each kind of income has its own page. The checklist below is our own arrangement of HMRC's notes for the current return, read from the position of a UK-resident American.
Two rules cut across the list. Employment income from abroad goes on the employment page, and the foreign pages are used only to claim credit for foreign tax on it. Gains on overseas assets go on the capital gains pages, never on SA106 itself, though the credit for foreign tax on a gain is claimed on SA106 and the gain has to appear in both places. The notes to the SA106 foreign pages (opens the official HMRC page in a new tab) set out both rules in their opening section.
HMRC also allows a few shortcuts, such as putting small amounts of untaxed foreign interest and dividends on the main return, which are unavailable where you claim credit for foreign tax or the four-year relief for new residents. For a US citizen whose Form 1040 reports every dollar anyway, keeping US items together on SA106 often makes the two returns easier to reconcile. Our UK Self Assessment service works through these choices.
- If you have a UK salary, a directorship or pay from a US employer with no UK payroll: SA102, one for each
- If you trade on your own account, including for US clients from a UK desk: SA103
- If you let property in the UK: SA105. If the property is in the US: the property section of SA106
- If you receive US interest, US dividends, a US pension, an IRA distribution or Social Security: SA106
- If you sold shares, funds or property anywhere: SA108, with any credit for foreign tax on the gain claimed on SA106
- If you arrived or left in the year, claim split-year treatment or foreign income relief, or are a treaty dual resident: SA109
Where do US interest, dividends and rent go on the SA106
All three go on SA106, in sterling, one row per country, with the code USA in the first column and the income entered before any foreign tax. What differs is the credit. The treaty decides how much US tax the UK will recognise for each type of income, and for bank interest that is usually none.
HMRC's notes tell you to check the dividend article of the relevant treaty, because it may limit the credit. For a UK resident, the treaty generally caps US tax on portfolio dividends at 15%, and Article 24 of the US-UK treaty (opens the official GOV.UK page in a new tab) adds a rule for citizens: the UK credits only the US tax that could have been charged on a UK resident who was not a US citizen. The US may tax an American's dividends at full citizen rates, but any double tax beyond the treaty level is relieved on the US side.
Interest works the other way. Under the treaty's interest article, interest owned by a resident of one country is taxable only in that country, so a UK resident's US bank interest is UK income with no UK credit for US tax. Rent from a US property is the opposite case. The treaty lets the US tax income from land located there, so the US tax on that rent is creditable through Foreign Tax Credit Relief (opens the official GOV.UK page in a new tab), entered in the SA106 section for property abroad.
A share sale belongs on SA108, not here. Under the treaty's gains article, gains on ordinary shares are taxable only in the seller's country of residence, so a UK resident usually has no US tax on the gain for HMRC to credit, even though the IRS taxes it as well. Our article on owning a US rental property while living in the UK covers the rental itself on both returns.
How do a US pension, an IRA and Social Security appear on the return
They go in the overseas pensions, social security benefits and royalties section of SA106. The treaty then decides whether the UK taxes each payment. US Social Security paid to a UK resident is taxable only in the UK, and regular pension payments generally follow the same residence rule, with exceptions that need checking payment by payment.
Article 17 of the treaty does the sorting. Social security paid by one country to a resident of the other is taxable only where the recipient lives, so US Social Security is UK income, converted to sterling. Regular payments from a US pension or IRA are also taxed in the country of residence, with a qualification: an amount the US would exempt if it were paid to a US resident is exempt in the UK as well. Lump sums are treated separately and are generally taxable only in the country where the scheme is established.
HMRC's notes say that where a treaty takes a pension out of UK tax, the payer, the pension and the relevant treaty should be described in the free-text box on the main return. Roth distributions and lump sums are where the question usually arises, and each turns on the plan's terms. Our US-UK pensions service works through them, and our post on US Social Security for UK residents covers the benefit in more depth.
When does a US citizen need the SA109 residence pages
When residence itself is part of the claim. HMRC's notes point to SA109 for anyone not UK resident, arriving during the year, claiming split-year treatment, making a foreign income and gains claim or an Overseas Workday Relief claim, and for treaty dual residence relief. A long-settled American with none of these normally leaves it out.
The foreign income and gains regime is where SA109 and SA106 meet. An American arriving after at least ten consecutive tax years of non-residence may claim relief on foreign income and gains for the first four tax years of UK residence. The claim is made on SA109, while the income is still reported on SA106 together with the amount being relieved. Relieved income carries no UK tax, so there is nothing for either credit to work on. Our guide for Americans in the UK sets out the cost in lost allowances.
The constraint is filing. HMRC's notes to the SA109 pages (opens the official HMRC page in a new tab) say that to send them online you need commercial software or an agent, and that they must not be attached as a file to a return sent through HMRC's own service. The alternative is paper, which is due by 31 October rather than 31 January. Treaty dual residents also need helpsheet HS302 (opens the official HMRC page in a new tab) and the claim form it contains. Our SA109 form guide explains the boxes.
Why is the UK return usually worked out before Form 1116
Because the treaty fixes the order. For a UK resident who is a US citizen, the UK first credits the US tax a non-citizen would have paid on US-source income. The US then credits UK tax on what remains, treating that income as UK-source to the extent needed. Form 1116 therefore depends on the finished UK figure.
Article 24 sets that sequence, and the US credit is applied after the UK one without reducing it. The UK computation produces the UK tax left on each US item after the UK credit, and those residual amounts are what the US side relieves on Form 1116, using the category for income re-sourced by treaty described in the Form 1116 instructions (opens the official IRS page in a new tab). Our post on which return to prepare first covers timing.
Take a US citizen employed in Edinburgh by a UK bank who lets a condominium in Denver, holds US shares through a US broker and keeps a US savings account. Her UK return is the SA100 with an SA102 for the salary and an SA106 carrying the Denver rent, the dividends and the interest. On the rent, HMRC credits the US tax. On the dividends, it credits US tax only up to the treaty rate. On the interest, it credits nothing at all.
Her US return then works from those results. The UK tax left on the dividends and interest is what the US relieves through the re-sourcing rule, alongside the UK tax on her salary. Our cross-border tax service prepares both returns from one set of figures.
General information, not advice. The right answer depends on your circumstances and the tax year concerned.
