Simon Roue and Laura Sant explain the UK Self Assessment tax return system in plain English.

Podcast recap: Tax Compass with LSR Partners
In this episode, Simon Rue and Laura Sand go 'straight down the middle of the fairway' on Self Assessment: when you must be in it, when you can get out of it, and the admin traps that create surprise penalties, especially for expats and non-residents.

Quick refresher: key dates

• UK tax year: 6 April to 5 April
• Online filing deadline: 31 January following the tax year
• Paper filing deadline: 31 October
• Coding-out deadline (collect <£3,000 via PAYE code): 30 December
• Payments on account (if applicable): 31 January and 31 July

You get clarity and confidence on cash flow when you file early, tax is still due 31 January, but you’ll know your number and can plan.

Who actually needs to file?

Common triggers for expats and globally mobile professionals include:

• Self-employment or partnership income
• UK rental income (generally >£1,000 gross)
• Dividend and investment income (particularly if >£10,000)
• Foreign income or gains that need reporting (e.g., remittance basis claims)
• Higher Income Child Benefit Charge
• Situations where tax wasn’t correctly collected at source

Removed income-only triggers: The old income threshold rule (e.g., £100k/£150k) has been phased out—now it’s more about types of income and untaxed income, not headline salary alone.

If you’re non-resident, don’t miss SA109

If you’re non-resident (or claiming the remittance basis), you must include SA109 (Residence). You can’t file SA109 via a standard Government Gateway DIY return, use commercial software or an adviser. If SA109 is missing, HMRC can reject your return or treat you as UK-resident by default. That’s how double taxation headaches start.

P85 when leaving the UK. Useful, but…

P85 can notify HMRC that you’ve left the UK but only if you’re not already in Self Assessment. If you are, HMRC will tell you to file a return to settle position and process any refund. Also note current paper P85 processing can be slow. Filing a return is often faster for refunds.

“Simple Assessment” vs Self Assessment

HMRC may send a Simple Assessment (e.g., where codes were wrong and you owe tax). If you receive one, you typically don’t have an open Self Assessment filing obligation. If you then need to disclose other items, you’ll likely have to ask HMRC to open a filing requirement, this is where LSR’s team shines.

Refunds for expats on UK payrolls; expect resistance

If you worked overseas while still on a UK payroll or moved mid-year, PAYE and Self Assessment systems don’t naturally 'talk.' Without an open filing requirement, HMRC often won’t release refunds. LSR’s 'SWAT' client service team reads the rules back to HMRC (politely but firmly) and gets the filing window opened so you can reclaim what you’re due.

Payments on account; when and how they bite

If your Self Assessment liability is >£1,000 and >20% of your total tax, HMRC asks for payments on account for the next year: 50% in January and 50% in July.
Good news: Capital Gains Tax, Class 2 NI, and Student Loans aren’t included in payments on account.

How to get out of Self Assessment (properly)

• Tick the 'final year' boxes for rental or self-employment in your last return
• If your situation no longer requires filing (e.g., only UK employment taxed via PAYE), request withdrawal of future filing obligations
• When leaving the UK: proactively withdraw your filing requirement (don’t assume split-year treatment does it) and ensure HMRC has your current address. Otherwise, penalties rack up silently.

Common expat pitfalls (and how you avoid them)

• Missing SA109: Your non-residence/remittance basis isn’t recognised. Fix by filing correctly.
• Assuming P85 alone handles refunds: If you’re in Self Assessment, file a return.
• Not withdrawing filing requirements: After leaving the UK, penalties can snowball.
• Paper deadlines and coding-out date confusion: 31 Oct (paper), 30 Dec (coding-out), 31 Jan (online & payment).
• DIY miscoding or wrong boxes: Automated refunds can be clawed back and trigger enquiries.

Listen to the episode

Need tailored advice?

You get strategic, expat-specific guidance so you pay the right tax in the right place. Book a clarity call with LSR Partners.

FAQs

Do I have to file if I’m non-resident but have UK rent?
Usually yes, especially if gross rent exceeds £1,000. You’ll also need SA109 for residence status.

Can I file SA109 via Government Gateway?
No. Use commercial software or a professional.

If I file early, do I have to pay early?
No. The payment deadline is still 31 January (plus 31 July for payments on account).

How do I stop getting tax returns after I move abroad?
Formally withdraw your filing requirement (and tick 'final year' where relevant). Don’t rely on split-year treatment alone.

This post is general guidance, not personal tax advice. Always take advice on your specific facts.

Contact LSR Partners today to speak with our expert team and pay the right tax, in the right place, at the right time.