Split-Year Treatment and Form SA109: Reporting the Year You Leave the UK

The year you actually move is the messy one. You were UK resident in April, you were living in Chicago by November, and HMRC's rules say you are either resident for the whole tax year or not resident at all. Split-year treatment is the relief that stops that being unfair, and form SA109 is how you claim it.

First: residence is decided for the whole year

Under the Statutory Residence Test you are resident or non-resident for a complete UK tax year (6 April to 5 April). If you are resident for the year of departure, split-year treatment then splits that year into a UK part and an overseas part, and you are only taxed on your worldwide income for the UK part. Foreign income and gains arising in the overseas part fall out of UK tax (UK-source income still does not).

The cases that apply when you leave

• Case 1 — starting full-time work overseas. You work full-time abroad for the rest of the tax year and the following tax year, within day limits. This is the most common case for someone taking a US job.
• Case 2 — partner of someone starting full-time work overseas. You join a spouse or partner who qualifies under Case 1.
• Case 3 — ceasing to have a UK home. You stop having any home in the UK, spend fewer than 16 days here afterwards, and become resident in the new country within six months.

If more than one case fits, HMRC's priority rules decide which one applies — and the case matters, because each has a different split date.

The forms: SA100, SA109 and friends

• SA100 — the main Self Assessment return.
• SA109 Residence, remittance basis etc. — the residence pages. This is where you tick that you were not resident, claim split-year treatment, state the case number and the split date, and give your day counts. Without SA109 your claim does not exist.
• SA105 — UK property pages, if you are letting the old home.
• SA106 — foreign income for the UK part of the year.
• SA108 — capital gains, including UK land and property disposals.
• NRL1 — the Non-resident Landlord Scheme application, so your letting agent or tenant pays rent gross instead of deducting 20% basic-rate tax.
• P85 — tells HMRC you have left, if you are not otherwise in Self Assessment.

One practical point that surprises people every single year: HMRC's own online Self Assessment service does not support SA109. If you need the residence pages you must either file on paper by 31 October or use commercial software or an agent to file online by 31 January. This is the single most common reason a departing client ends up filing late.

Worked example: Sarah's year of departure

Sarah, a US/UK dual citizen, leaves London on 30 September 2026 and starts full-time work in Boston on 12 October 2026. Her tax year 2026/27 income is:

• UK salary 6 April – 30 September 2026: £48,000 (PAYE deducted).
• US salary 12 October 2026 – 5 April 2027: $95,000.
• UK rent from the Clapham flat, 1 November 2026 onwards: £9,000 gross.
• US brokerage dividends after the move: $3,200.

UK treatment. Sarah qualifies for split-year treatment under Case 1. The UK part runs to 30 September 2026 and the overseas part from 1 October 2026.

• Her UK salary of £48,000 is taxed in the UK — normal PAYE, probably with a refund because she used only half a year of the personal allowance against a full year's tax code.
• Her US salary is in the overseas part, so it is not taxed by the UK.
• Her US dividends are in the overseas part and are not taxed by the UK.
• Her UK rent is taxed in the UK even after she leaves, because it is UK-source. She files SA105, and applies on NRL1 so the agent stops withholding.

Her 2026/27 return is: SA100 + SA109 (Case 1, split date 30 September 2026, day counts shown) + SA105 for the rent. Filing deadline 31 January 2028 online, or 31 October 2027 on paper.

US treatment. As a US citizen Sarah reports everything on Form 1040 for calendar year 2026 — the UK salary, the US salary, the UK rent and the dividends. She avoids double tax on the UK-taxed items using the foreign tax credit on Form 1116, and she reports her UK bank and pension accounts on FinCEN Form 114 (FBAR) and, if thresholds are met, Form 8938.

Note the calendar-versus-fiscal mismatch: the UK year ends 5 April, the US year ends 31 December. Getting the credits to line up is most of the work in a departure year, and it is why we prepare both returns together rather than in isolation.

Non-resident filing after the move

Once you are fully non-resident you still file a UK return for any UK-source income. Two rules matter most:

• Disregarded income. UK dividends and interest can, in some circumstances, be "disregarded" for a non-resident, capping the UK tax at the amount withheld — but taking that treatment can cost you the personal allowance. It needs a calculation both ways, not a rule of thumb.
• The personal allowance. British citizens and other qualifying persons keep the UK personal allowance while non-resident, which often shelters modest rental profits entirely.

Common mistakes we are asked to correct

• Filing the SA100 without the SA109 — HMRC then taxes the whole year as UK resident.
• Claiming the wrong split-year case, so the split date is wrong by weeks or months.
• Missing NRL1 and losing cash flow to 20% withholding for a year.
• Reporting the departure year to the IRS on a calendar-year basis while claiming credits on a UK fiscal-year basis, and mismatching the two.
• Forgetting the 60-day UK property CGT return when the old home is sold after leaving.

If you are leaving in the current tax year, the time to model this is before you go, not the following January. A 30-minute consultation is £150; a fixed fee for the work follows in writing.