What is the SA109 form?

What SA109 is

The main UK Self Assessment return is form SA100. Anything that does not fit on it goes on numbered supplementary pages: SA102 for employment, SA105 for UK property, SA106 for foreign income and so on. SA109 is the residence supplement — its full title is “Residence, remittance basis etc”. It is where you tell HMRC what your residence status was for the tax year under the Statutory Residence Test (SRT), and where you make any claims that depend on that status.

There is one practical quirk that catches many people out: HMRC’s free online Self Assessment service does not support the SA109 pages. If you need them, you either file the whole return through commercial tax software that includes SA109, or you file on paper. Filing the SA100 online and posting the SA109 separately is not an option — the return must be submitted as one.

Who has to file it

You need SA109 for a tax year (6 April to 5 April) if any of the following apply and you are within Self Assessment:

• You were not UK resident for the year under the SRT but still have to file a return — for example because you have UK rental income, UK self-employment, or a UK-source capital gain.
• You claim split year treatment because you arrived in or left the UK part-way through the year and fit one of the eight RDR3 cases.
• You were dual resident — resident in the UK under the SRT and in another country under its domestic law — and you are claiming that a double taxation agreement treats you as resident in the other country.
• You are claiming the remittance basis of taxation on foreign income and gains (tax years up to 2024–25), or, from 2025–26, the four-year foreign income and gains regime that replaced it.
• You are a non-resident claiming UK personal allowances on the basis of nationality or residence in a qualifying country.

If you were UK resident for the whole year, make none of these claims, and have no domicile or remittance position to report, you generally do not need SA109 at all.

The key boxes

The form is short but every box is a factual statement about your year, and most of them are numbers you can only get from a day-by-day record. The boxes that matter most:

• Residence status. Whether you were not resident for the year, and whether you were UK resident in the previous tax year — the second answer determines whether you are an “Arriver” or a “Leaver” for the ties table.
• Split year claim. A box to confirm your circumstances meet the split year criteria, the case you rely on, and the date the UK part of the year starts or ends.
• Days in the UK. The number of days you spent in the UK in the year, counted on the SRT midnight basis, plus a separate box for days you want disregarded under the exceptional-circumstances rule (maximum 60).
• UK workdays. The number of days on which you did more than three hours’ work in the UK — needed for the work tie and for the third automatic overseas test.
• Ties. How many UK ties you had in the year under the sufficient ties test, and whether you had a home overseas.
• Treaty claim. Whether you were also resident in another country under its rules, and whether you are claiming treaty residence there under the tie-breaker article.

How SA109 connects to the SRT day counts

SA109 does not ask HMRC to decide your residence — it asks you to state it and to give the numbers that back it up. Those numbers are the three SRT counts:

1. 1UK days — days on which you were in the UK at midnight, less any days disregarded for exceptional circumstances, plus any days added by the deeming rule.
2. 2UK workdays — days on which you did more than three hours' work in the UK, whether or not you stayed overnight.
3. 3Ties — the family, accommodation, work, 90-day and (for Leavers) country ties, several of which depend on day counts from this year and the two before it.

Because the ties test looks back two tax years and the automatic tests look back three, a single year’s SA109 can depend on up to four years of travel history. HMRC can ask for evidence — tickets, boarding passes, diary entries — for any of those figures, so the day count you enter should be one you can reproduce. The UK SRT calculator produces the UK-day and workday totals from your trip dates on the midnight basis SA109 expects.

Deadlines

• Paper return (SA100 with SA109 attached): 31 October following the end of the tax year.
• Online return through commercial software that supports SA109: 31 January following the end of the tax year — the same date any tax due must be paid.

Miss the paper deadline and you can still file online by 31 January without a late-filing penalty, provided the software route is open to you. If you only realise you needed SA109 after filing an SA100 online, you amend the return by refiling it in full, with the residence pages included, within the normal amendment window.

Common errors

• Leaving SA109 out. Filing an ordinary online return as a non-resident, with no residence pages, tells HMRC nothing about your status — and by default a return with no SA109 is read as a resident return.
• Counting the wrong days. Entering days on which you were present at any time (the “any part of a day” basis used by many other countries) rather than days on which you were in the UK at midnight, or counting over the calendar year instead of 6 April to 5 April.
• Inconsistent figures. Claiming non-residence while entering a day count and tie count that, read against the ties table, make you resident. HMRC checks the boxes against each other.
• Claiming split year without a case. Ticking the split year box because you moved, when none of the eight cases applies — leaving mid-year with a UK home still available is the classic example.
• Forgetting workdays. Day trips for meetings that ended before midnight add UK workdays without adding UK days. Forty of them create a work tie; thirty-one breach the full-time-work-abroad test.

Why a day-by-day record helps

Every numeric box on SA109 is the output of a calendar. A record that logs each UK entry and exit — and flags which days involved more than three hours of UK work — lets you fill in UK days, exceptional days, workdays and the 90-day tie without reconstruction, and gives you something to show HMRC if the figures are queried years later. Bounded keeps that record automatically from your location history and counts it on the UK tax-year, midnight-rule basis; the free Statutory Residence Test calculator does the same from dates you type in.

Sources

• GOV.UK — Self Assessment: Residence, remittance basis etc (SA109)
• HMRC — RDR3: Statutory Residence Test (SRT)
• GOV.UK — Tax on foreign income: UK residence and tax