SA100 Tax Return Guide: Which Supplementary Pages Cross-Border Filers Need

This SA100 tax return guide starts from one fact: the SA100 is only the eight-page core of a UK return, and each kind of income outside it sits on a supplementary page. Cross-border filers usually need SA102, SA105, SA106, SA108 or SA109 on top, and the SA109 cannot be filed through HMRC's own online service. Picking the right pages is the first decision of the return.

This guide maps the main return and every supplementary page for the 2025/26 tax year (6 April 2025 to 5 April 2026), then lets you read off the pages for your own situation. Titles, thresholds and box numbers come from HMRC's SA100 form and notes for 2025 to 2026 and the notes to each page.

What is the SA100 tax return, and what does it cover on its own?

The SA100 is the main Self Assessment tax return for individuals. The 2025/26 form runs from page TR 1 to TR 8. On its own it covers UK interest and dividends, UK pensions and state benefits, pension and Gift Aid reliefs, student loan repayments, the High Income Child Benefit Charge and the signed declaration.

Everything else is bolted on. Page TR 2 asks nine questions, and HMRC's notes are direct about the consequence: if you put an X in any Yes box, you must fill in and send the supplementary pages for that income or gain, and if you do not, "we'll treat your tax return as incomplete and send it back to you".

One concession matters to people with modest US accounts. If your only foreign income is untaxed foreign interest of up to £2,000 or foreign dividends of up to £500, the 2025/26 notes let you enter them in boxes 3 and 6 on page TR 3 instead of completing the Foreign pages. The shortcut does not apply if your total dividends are over £500 and you want relief for the foreign tax on them, or if you are claiming FIG relief on the income.

The SA100 supplementary pages for 2025/26 at a glance

GOV.UK's list of Self Assessment forms and supplementary pages gives each page a number. The table adds which cross-border filers usually need it.

Page	Title (2025/26)	What goes on it	Cross-border filers who need it
SA101	Additional information	Share scheme income, employer lump sums, gilt interest, life policy gains, pension savings tax charges	Employees with share awards; split-year filers with foreign earnings not taxable in the UK (box 12)
SA102	Employment	Pay, tax deducted, benefits and expenses, one page per job or directorship	Anyone employed in the UK; UK residents paid by a US employer
SA103S / SA103F	Self-employment (short / full)	Turnover, expenses and profit of a sole trade	Freelancers with UK or US clients
SA104S / SA104F	Partnership (short / full)	Your share of partnership profit	Partners in UK or foreign firms
SA105	UK property	UK rents, expenses, finance costs	Non-resident landlords; anyone letting a UK home after leaving
SA106	Foreign	Foreign interest, dividends, pensions, overseas property and foreign tax credit relief	UK residents with US income
SA107	Trusts etc	Income from a trust, settlement or estate; settlor-attributed income	Beneficiaries and settlors of trusts
SA108	Capital Gains Tax summary	Disposals, gains, losses and claims	UK residents selling US assets; non-residents selling UK land
SA109	Residence and foreign income and gains (FIG) regime etc	Non-residence, arrival, split year, FIG claims, treaty relief	Arrivers, leavers, non-residents, FIG claimants
SA110	Tax calculation summary	The result of your own tax calculation	Paper filers who calculate the tax themselves

The 2025/26 SA109 is titled "Residence and foreign income and gains (FIG) regime etc". Earlier versions were called "Residence, remittance basis etc", and some GOV.UK index pages still show the old name.

The pages cross-border filers use most

SA102 Employment

You need one Employment page for each job, directorship or office. The 2025/26 notes include people who "were resident in the UK and received an income from any foreign employment". A UK resident on a US payroll therefore reports the salary on the SA102, in pounds, and uses the SA106 only to claim credit for any US tax on it.

SA105 UK property

The UK property pages are needed when property income is over £1,000 for 2025/26, counting UK and foreign property together. They are also where a landlord living abroad reports UK rent. Under the non-resident landlord scheme, GOV.UK explains that a letting agent, or a tenant paying more than £100 a week, deducts basic rate tax from the rent unless HMRC has approved gross payment. Box 21 of the SA105 is where that tax is claimed back.

SA106 Foreign

The Foreign pages carry foreign interest above £2,000, foreign dividends above £500, overseas pensions and social security, income from land and property abroad, and claims for Foreign Tax Credit Relief. HMRC's notes also place discretionary income from non-resident trusts here, not on the SA107, which catches beneficiaries of US family trusts. We have a box-by-box guide to the SA106 foreign income pages and a separate one on how US citizens report US income to HMRC.

SA108 Capital Gains Tax summary

For 2025/26 the Capital Gains Tax summary pages are required if you disposed of chargeable assets worth more than £50,000, if your gains before losses were more than £3,000, or if you want to claim a loss or make a capital gains election. They are also required if you disposed of an interest in UK land or property while non-resident, or in the overseas part of a split year. Non-residents have a second duty: GOV.UK says disposals of UK property or land must be reported within 60 days even where there is no tax to pay.

SA101 Additional information

The SA101 is the page people forget. It holds share scheme income, employer lump sums and pension savings tax charges, including those on overseas pension schemes. Box 12, "Foreign earnings not taxable in the UK", is the one that matters in a year of arrival or departure. The notes say you need helpsheet HS211 to work out the figure if you are non-resident or claiming split-year treatment.

Who needs the SA109 residence pages?

The SA109 is needed by anyone whose UK tax position depends on residence. The 2025/26 notes list them: people who are not resident in the UK, and UK residents who became resident during the year, are due split year treatment, or want to claim FIG relief, Overseas Workday Relief, a temporary repatriation facility designation or Business Investment Relief. A return filed without the SA109 is processed as the return of a full-year UK resident.

Most filers touch only a few boxes of the 2025/26 SA109:

• Box 1: an X if you were not resident in the UK for 2025/26. Boxes 7 to 13 then record the facts behind that status, such as days in the UK and UK ties. See our Statutory Residence Test guide.
• Boxes 3 and 6: split year treatment and the date the UK part of the year begins or ends, with the case number written in box 54. See the eight split year cases.
• Boxes 15 and 16: a claim to personal allowances as a non-resident, under a treaty (box 15) or on another basis such as being a British citizen or an EEA national (box 16).
• Boxes 20 to 22: relief claimed under a double taxation agreement.
• Boxes 23, 24, 28 and 29: date of arrival, last year of UK residence, and the separate claims for relief on foreign income and on foreign gains under the four-year FIG regime.
• Boxes 40 to 49: the Overseas Workday Relief election and claim. The notes warn that an election removes the personal allowance and the capital gains annual exempt amount for that year.

A point for Americans who have left the UK: the box 15 list of treaty countries in the 2025/26 notes does not include the United States. A US citizen landlord living in America has no route to the UK personal allowance through box 15 and needs to fit a box 16 category, such as British citizenship, to claim it.

Treaty claims: HS304 and HS302

A non-resident who wants UK income relieved under a treaty uses helpsheet HS304. HMRC lists the income it can cover as bank and building society interest, royalties, most work pensions, annuities and UK dividends. The income for which partial relief is claimed goes in box 20 and UK tax already deducted in box 22, and the claim form inside the helpsheet is sent with the return. UK rental income is not on that list, because Article 6 of the US/UK double taxation convention leaves the UK free to tax income from UK property.

A dual resident, meaning someone resident in the UK under domestic law and also in another country, uses helpsheet HS302. It walks through the treaty tests in order: permanent home, centre of vital interests, habitual abode, nationality. Where they award residence to the other country, the UK tax relieved goes in box 21. Our article on the treaty tie-breaker rule explains the tests, and our treaty relief service prepares the claims.

Your situation: which SA100 supplementary pages do you need?

Find the row closest to your 2025/26 facts. Every row also needs the main SA100.

Your situation in 2025/26	Pages you are likely to need	Watch for
American employee, UK resident all year, with US dividends or interest above the TR 3 limits	SA102, SA106	SA108 if you sold US shares; SA101 for share scheme income
American who arrived in the UK during the year	SA102, SA106, SA109	Boxes 3 and 6 if a split year applies
New arrival claiming FIG relief or Overseas Workday Relief	SA109, SA106, SA108, SA102	Relieved income still reported on SA106 and gains on SA108; allowances lost for the year
Brit who moved to the US part way through the year	SA102, SA109, possibly SA101	Split year case in box 54; SA105 if the UK home is now let
Non-resident landlord living in the US	SA105, SA109	Box 1 for non-residence; box 21 of SA105 for tax deducted from rent
Non-resident with a UK pension, interest or dividends claiming treaty relief	SA109 plus HS304 claim form	Boxes 20 and 22
UK resident under the Statutory Residence Test but treaty resident in the US	SA109 plus HS302 claim form	Box 21
Self-employed in the UK with US clients	SA103S or SA103F	Full pages if turnover is £90,000 or more

Not sure you are in Self Assessment at all? Start with whether you need to file a UK return, then how it fits with the US one.

Illustrative example: a British citizen leaves London on 1 August 2025 to start a full-time job in New York and lets her London flat from September. For 2025/26 she is UK resident with a split year, so her return is the SA100 with an SA102 for her UK job to July, an SA105 for the rent and an SA109 with an X in boxes 3 and 4, the split date in box 6 and Case 1 named in box 54. For 2026/27 she is non-resident: SA100, SA105 and an SA109 showing non-residence (box 1 on the 2025/26 form) with a personal allowance claim as a British citizen (box 16). Neither return can go through HMRC's own online service. This is illustrative only; the right pages depend on the actual facts.

How do you file an SA100 that includes the SA109?

You file it with commercial software, through an agent, or on paper. The 2025/26 SA109 notes say that to submit the pages online "you'll need to purchase software from a commercial supplier, or authorise a professional agent to file your tax return on your behalf". They must not be sent as an attachment to an online return.

GOV.UK's online filing page says the HMRC service cannot be used "if you lived abroad as a non-resident", for a partnership, a trust or estate, or if you get income from a trust. Its guidance on tax on UK income if you live abroad gives the same three routes.

The restriction is wider than non-residents. A UK resident with a split year or a FIG claim also needs the SA109, and so also needs software or paper. Our SA100 tax return service files through agent software with the SA109 included.

SA100 deadlines for the 2025/26 tax year

These dates are from GOV.UK's Self Assessment deadlines page and the 2025/26 notes.

1. 5 October 2026: tell HMRC if you need to complete a return for 2025/26 and have not filed before. See our guide to registering by 5 October.
2. 31 October 2026: paper returns, including a paper SA109, must reach HMRC by 11:59pm.
3. 30 December 2026: online filing date if you want tax collected through your PAYE code.
4. 31 January 2027: online returns, including those filed through commercial software, and payment of the tax owed for 2025/26.
5. 31 July: the second payment on account, where payments on account apply.

If HMRC issued your notice to file late, the notes allow three months from the date of the notice where that is later. The notes set the initial late filing penalty at £100 even if no tax is owed, with further penalties once a return is more than 3, 6 and 12 months late. A non-resident who misses the paper deadline can still file on time, but only through commercial software or an agent.

What cross-border filers get wrong on the SA100

• Putting foreign salary on the SA106. Employment income goes on the SA102 wherever the employer is. The SA106 only carries the foreign tax credit claim for it.
• Filing through HMRC's online service and leaving the SA109 out. The return goes through, but HMRC then taxes you as resident for the full year with no split, no FIG claim and no treaty relief.
• Reporting a foreign gain on the Foreign pages. The gain goes on the SA108. The SA106 is used only for the foreign tax on it.
• Assuming the personal allowance follows you abroad. A non-resident has to claim it in box 15 or 16 of the SA109, and US nationality alone does not appear in either list.
• Claiming treaty relief without the claim form. Boxes 20 to 22 need the HS304 or HS302 form sent as well.

Getting the pages right before the numbers

An SA100 with the wrong pages is wrong before a single figure is entered. Fix your residence status for the year first, because it decides whether the SA109 is needed and so how the return can be filed. Then list each source of income and gain against the table above.

US/UK Cross Border Tax — US CPAs and UK tax advisers working as one team; London, Manchester, New York, San Francisco. We prepare UK returns for Americans in the UK and for landlords living abroad with the US return in view. If you are unsure which pages your 2025/26 return needs, get in touch.