Leaving the UK P85 or Final Self Assessment Return?

If you leave the UK part-way through a tax year, you file either a Form P85 or a final Self Assessment return with the SA109 residence pages — not both routes for the same purpose. The P85 is a notification and a PAYE refund claim. Only the Self Assessment return formally claims split-year treatment and closes the UK year properly.

For an American, that choice is rarely as simple as HMRC's own decision tree suggests. A US citizen or green card holder who has been living in London almost always has something in the picture — a US brokerage account, a rental flat left behind, restricted stock that vests after the flight, a self-employment schedule, a pension in payment — that pushes the departure year out of P85 territory and into a full final return. Getting the leaving the UK P85 decision right at the outset determines whether your split-year claim is on the record at all, and whether HMRC's repayment matches the number your US return will need to see. At Jungle Tax we prepare the final UK return and the US return for the same departure as one file, because they are one economic year cut two different ways.

P85 or a final Self Assessment return: which route applies?

HMRC's guidance is short and easily misread. The operative sentence on the P85 guidance page is that you do not need to complete the form if you are sending a Self Assessment tax return for the tax year in which you leave. That is the fork in the road. Everything else follows from whether a return is required.

When the P85 is genuinely the right route

The P85 is designed for a narrow profile: someone taxed entirely through PAYE, leaving the UK permanently or to work full-time abroad for at least a complete tax year, with no other reportable income and no existing Self Assessment record. The form tells HMRC you have gone, gives them the departure date and the P45 figures, and asks them to recalculate the year on the assumption that the personal allowance now sits against a part-year salary. The result is usually a repayment, because PAYE has been spreading the allowance evenly across twelve months that you did not complete.

Practically, the online service is only open once you have actually left. If you file before departure you must post the paper form with parts 2 and 3 of the P45 to the PAYE office at BX9 1AS. HMRC issue repayments by payable order, which is why the guidance quietly advises keeping a UK bank account open until the money arrives.

When a final Self Assessment return is compulsory

A return is required for the departure year — and the P85 becomes redundant — if any of the following are true in the UK part of the year, or after it:

• You are already registered for Self Assessment and have not been formally taken out of it. A live record generates a notice to file; ignoring it generates penalties regardless of whether tax is due.
• You have self-employment or partnership income, UK rental income, or profits from a trade carried on in the UK.
• You have untaxed investment income, foreign income, or dividends above the dividend allowance.
• You realised chargeable gains above the annual exempt amount, or disposed of UK land or property at any gain as a non-resident.
• You have income above the level at which HMRC require a return for higher earners, or the High Income Child Benefit Charge applies.
• You are claiming split-year treatment, the remittance basis for years before its abolition, or relief under the US–UK double tax treaty on the return.
• You have employment-related securities — options, RSUs, growth shares — that vest or are exercised around the departure date with UK workdays in the vesting period.

That last category catches most departing executives and founders. If any of it applies, the P85 does not help you and filing it can actively confuse matters: HMRC may issue a PAYE repayment that the final return then has to claw back.

Can you sensibly do both?

Some advisers file a P85 alongside a return to accelerate the refund and force an address change onto HMRC's record. It is not wrong, but it is not free: two workstreams describing the same year can produce two different residence conclusions in HMRC's systems, and the repayment released against the P85 will be reconciled against the return months later. Our preference for US-connected clients is a single, well-evidenced final return, with a separate written notification of the new overseas address and the departure date. If the departure year is simple enough that a P85 alone would do, the client usually is not our client.

How is the split-year claim actually made on the final return?

Split-year treatment is not automatic and it is not claimed on the P85. It is claimed on the SA109 supplementary pages, filed with the SA100. The current form is titled Residence and foreign income and gains (FIG) regime etc, reflecting the replacement of the remittance basis with the four-year FIG regime from 6 April 2025.

The mechanics on the leaver's SA109 are narrow and unforgiving:

• You tick the box confirming you were not resident in the UK for the year, or were resident but claiming split-year treatment.
• You tick the split-year box and state the number of the Case relied on.
• You enter the date on which the UK part of the year ended — the split date.
• You state days spent in the UK, workdays, and the country of residence claimed for the overseas part.
• Where treaty residence is claimed, you complete the treaty non-residence section and identify the country.

Which departure Case applies?

The Statutory Residence Test provides eight split-year Cases; three of them are leaving cases. Full mechanical detail sits in HMRC's RDR3 guidance on the Statutory Residence Test, and the ordering matters because more than one can be satisfied at once.

Departure Case	Broad trigger	Where the split date falls
Case 1	You start full-time work overseas, and satisfy the overseas work criteria for the relevant period	The day the overseas employment begins
Case 2	You are the partner of someone meeting Case 1 and you join them abroad	The later of your departure to join them and the start of their overseas work
Case 3	You cease to have any home in the UK, and meet the subsequent tests on ties and days	The day you no longer have a UK home

Where more than one leaving Case is met, Case 1 takes priority over Case 2, and Case 2 over Case 3. That priority is not cosmetic: the Cases produce different split dates, sometimes weeks apart, and the split date is the hinge on which every subsequent allocation of income turns. An American who resigns in June, keeps the Notting Hill house on the market until September, and starts a New York role in July may have a Case 1 date in July and a Case 3 date in September. Case 1 wins, and three months of US-source income you assumed was outside the UK net is not.

Filing route and deadlines for the departure year

HMRC's own free online Self Assessment service does not support the SA109. A departing taxpayer therefore has exactly two routes: a complete paper return by 31 October following the end of the tax year, or an electronic return through commercial software by the following 31 January. There is no third option, and the paper deadline is the one that catches people who assume they have until January. We cover the timing collision between that date and the US extended deadline in our guides library.

What the P85 cannot do

It is worth stating the limits plainly, because the form's simplicity is misleading:

• It does not claim split-year treatment. It prompts an informal PAYE recalculation, not a statutory claim.
• It does not record your Case, your split date, or your day counts — so nothing is on the record if HMRC later query residence.
• It does not report rental income, gains, foreign income, or securities events.
• It does not remove you from Self Assessment. Only HMRC can close a record, and only on request.
• It does not register you for the Non-resident Landlord Scheme if you keep a UK property.
• It produces no filed document you can hand to the IRS as evidence of UK tax paid.

What income stays inside the UK net after departure?

Split-year treatment removes your foreign income and gains from UK charge for the overseas part of the year. It does not make you invisible to HMRC. As the GOV.UK guidance for people living abroad sets out, UK-source income remains chargeable.

• UK employment income for UK workdays. Earnings referable to duties performed in the UK stay taxable even if paid after you leave. A bonus paid in December for a performance year worked largely in London is apportioned, not exempted.
• Employment-related securities. Options and RSUs are apportioned by reference to UK workdays over the relevant period. Vesting after departure does not sever the UK slice.
• UK rental income. Taxable throughout. If you retain the property, the tenant or letting agent must deduct basic rate tax at source unless you obtain HMRC approval to receive rent gross under the Non-resident Landlord Scheme.
• UK land and property gains. A non-resident disposal of UK land or property must be reported and the tax paid within 60 days of completion, separately from and in addition to the annual return.
• UK pensions. Taxable in the UK by default; treaty relief must be claimed, and the US–UK treaty treats government service pensions differently from private pensions.
• UK dividends and interest. These fall within the "disregarded income" rules for non-residents. In broad terms you can elect to leave them out of the UK computation, but the price is the personal allowance. The comparison has to be run both ways for the departure year, and the answer varies with the size of the pre-departure salary.

How does the final partial UK year line up against a full US calendar year?

This is the part generalist UK pages leave out entirely, and it is where the money is. Your UK year ends 5 April. Your US year ends 31 December. A departure in, say, September 2026 sits inside UK tax year 2026-27 and inside US tax year 2026 — but those two containers hold different slices of the same life.

Feature	UK / HMRC	US / IRS
Tax year	6 April to 5 April	1 January to 31 December
Effect of leaving	Residence can be split mid-year under the SRT	None — citizenship-based taxation continues for life
Departure year filing	Final return with SA109, or P85 if no return is due	Form 1040 for the full calendar year, as normal
How the claim is made	Split-year Case and split date on SA109	Form 2555 exclusion and/or Form 1116 credit
Main deadline	31 October (paper) or 31 January (software)	15 April, automatic to 15 June abroad, extendable to 15 October
Foreign asset reporting	Not applicable	FBAR and, where thresholds are met, Form 8938
Currency	Sterling	US dollars, translated at appropriate rates

The exclusion trap in the year you leave

Americans working in London commonly rely on the foreign earned income exclusion. In a departure year it frequently breaks. Under the IRS guidance on the foreign earned income exclusion, you qualify either as a bona fide resident of a foreign country for an uninterrupted period including an entire tax year, or by being physically present in a foreign country for at least 330 full days in any twelve consecutive months.

Leave in September and the bona fide residence test fails for the year of departure — you were not a foreign resident for the whole calendar year. The physical presence test may still be met using a twelve-month window that begins in the prior year and straddles the departure, but the exclusion is then prorated by the number of qualifying days falling within the calendar year. The cap itself is indexed annually and applies to the full-year figure, so a nine-month qualifying period yields roughly three-quarters of it. Housing exclusions prorate on the same basis. Structuring the departure date around the 330-day count is one of the few genuinely valuable moves available, and it is only available before you fly.

Credit timing, and why the two systems disagree

Where the exclusion is unavailable or insufficient, the foreign tax credit does the work. Form 1116 claims credit for UK tax paid or accrued. The difficulty in a departure year is timing. UK tax on the final part-year is not settled until the return is filed, months after the US return is due. Elect the accrual method and you must apply it consistently thereafter. Stay on the paid basis and the credit lands in the following US year, potentially against a year with little foreign income to shelter it — creating an unusable carryforward at precisely the moment you needed a credit.

The other structural mismatch is sourcing. UK tax computed on a part-year basis attaches to a different income set than the calendar-year US return. Allocating UK tax between US general and passive baskets, and between the pre- and post-departure periods, is a modelling exercise rather than a transcription exercise. It is the single most common place we see prior-year returns overpay. Our cross-border tax planning work on departure years is largely this.

Reporting obligations that do not end at the airport

Leaving the UK does not close the American's file. UK bank accounts, ISAs, and any pension retained after departure remain reportable on the FBAR and, where thresholds are met, on Form 8938. An ISA is not tax-free to the IRS, and a stocks and shares ISA holding UK-domiciled funds carries passive foreign investment company exposure regardless of where you now live. Departing clients who have never filed these forms should read our note on IRS streamlined filing before the departure year return is prepared, because the sequencing of a disclosure and a departure return matters.

A practical sequence for the departure year

• Before you go. Fix the departure date against both the SRT leaving Cases and the US 330-day window. Record days, workdays, and accommodation contemporaneously. Determine whether the UK home is retained, sold, or let.
• At departure. Obtain the P45. Notify your employer of the change in payroll treatment for post-departure duties. If a property is retained, apply under the Non-resident Landlord Scheme before the first post-departure rent is due.
• Immediately after. Notify HMRC of the overseas address. Decide the route: P85 only, or final return. If a return is due, confirm whether you are filing on paper by 31 October or through commercial software by 31 January.
• Before the US deadline. Model the exclusion and credit positions on provisional UK figures. Decide paid versus accrued. Extend the US return if the UK numbers will not be final in time.
• On filing. File the SA100 with SA109, claiming the correct Case and split date, and reconcile the sterling and dollar figures across both returns so they tell the same story.
• Afterwards. Ask HMRC to close the Self Assessment record only once every post-departure UK source has genuinely ended. Reduce or cancel payments on account where the following year's UK liability will be lower.

Where departure years go wrong

The recurring failures we are asked to unwind are consistent. Filing a P85 when a return was required, and treating the resulting refund as confirmation that the year is closed. Claiming split-year treatment on the wrong Case, and therefore the wrong split date. Assuming that income paid after departure is automatically outside the UK net, when apportionment by workday says otherwise. Letting a UK property without registering under the Non-resident Landlord Scheme. Missing the 60-day non-resident property gain report. Filing the US return on the assumption that a full exclusion is available in the departure year. And, most expensively, filing the two returns in isolation, so that the UK tax claimed as a US credit does not match the UK tax actually assessed.

None of these are exotic. They are the ordinary consequence of a UK adviser and a US adviser each doing competent work on half a year. Our UK tax services and US filing teams work the departure year as a single engagement for exactly that reason, and our US and UK tax accountants prepare both returns from one set of figures.

Speak to us before you file the final year

If you are leaving the UK this year, or have already left and are unsure whether a P85 or a final Self Assessment return closes your UK position properly, the decision is worth an hour now rather than a correction later. We prepare final UK returns with split-year claims and the matching US return for Americans, executives and founders leaving the UK, and we will tell you plainly which route your year requires. To review your departure year in confidence, contact our cross-border team for a confidential consultation.