The UK Tax Year Calendar: Key Dates and Deadlines for Expats

The UK has one of the most convoluted tax year structures in the world. The tax year runs from 6 April to 5 April — a legacy of calendar changes in 1752 that left the Exchequer unwilling to lose 11 days of tax revenue. Add to this multiple different deadlines for filing, payment, and specific asset types, and the result is a calendar that trips up even experienced taxpayers.

For internationally mobile individuals, the stakes are higher. Missing deadlines can trigger automatic penalties, interest charges, and — in extreme cases — HMRC enquiries. This guide sets out the key dates in clear terms.

The Tax Year: 6 April to 5 April

Every UK tax year runs from 6 April to 5 April of the following year. The tax year 2025/26, for example, runs from 6 April 2025 to 5 April 2026.

Why this matters for expats: the Statutory Residence Test (SRT) assesses UK residence on a tax-year basis. If you spend enough days in the UK to become resident in a given tax year, you are treated as UK resident for the whole year — unless split-year treatment applies (which can divide the year into a UK part and an overseas part).

Counting your UK days carefully relative to the 5 April year-end is essential for managing residence status.

Self-Assessment: The Core Deadlines

Self-assessment is the system by which individuals with complex tax affairs — including overseas income, capital gains, director's income, and others — report their income and gains to HMRC.

Key self-assessment deadlines:

Deadline	Date	What It Covers
Register for self-assessment	5 October (year after tax year)	First time filers and new sources of income
Paper return deadline	31 October	Self-assessment return filed on paper
Online return deadline	31 January	Self-assessment return filed online
Tax payment (balancing)	31 January	Tax owed for the previous tax year
First payment on account	31 January	Advance payment for current tax year
Second payment on account	31 July	Second advance payment for current tax year

For example, for the 2025/26 tax year (6 April 2025 to 5 April 2026):

• Register by 5 October 2026
• File online by 31 January 2027
• Pay balancing payment by 31 January 2027
• First payment on account for 2026/27 also due 31 January 2027
• Second payment on account for 2026/27 due 31 July 2027

Payment on Account Explained

Payments on account are advance payments of income tax and Class 4 National Insurance Contributions for the coming tax year, based on the previous year's liability. They apply where your last self-assessment liability was £1,000 or more (and was not fully covered by tax deducted at source).

Each payment on account is 50% of the previous year's liability. If your actual liability for the current year is higher, a balancing payment is due on 31 January; if lower, you receive a refund or credit.

For expats: if your income is variable — which is common for internationally mobile individuals with investment income, foreign earnings, and property rents — you can apply to reduce payments on account where you reasonably expect your liability to be lower than the previous year. This is done via form SA303 or through the HMRC online account. Incorrect reduction can lead to interest charges.

Overseas Income on the SA Return

UK tax residents must declare worldwide income on the self-assessment return. This includes:

Foreign employment income (SA102F): earnings from an overseas employer, including benefits in kind (company car, medical insurance, school fees). If tax was paid overseas, a credit is generally available under the relevant double tax treaty.

Foreign investment income (SA106): dividends from overseas companies, interest on foreign bank accounts, income from overseas investment platforms. Must be converted to sterling at the exchange rate at the date of receipt (or HMRC's published rate for the year).

Foreign property income (SA105/SA106): rents from overseas properties, net of allowable expenses. This is a commonly missed or underdeclared category.

Foreign pension income (SA106): overseas pension payments, whether from state pensions (e.g., Cypriot or UAE-source pension income) or occupational schemes. Treaty treatment varies significantly.

Automatic penalties for late filing of self-assessment returns start at £100 even if no tax is owed. Daily penalties of £10 per day apply after three months, capped at £900. Six-month and 12-month late returns attract further penalties of 5% of tax owed.

Capital Gains Tax: The 60-Day Rule for UK Property

From 27 October 2021, UK residents (and non-residents) who dispose of UK residential property must:

1. Report the gain (or loss) to HMRC using the UK Property Reporting Service
2. Pay any CGT due within 60 days of completion

This 60-day deadline is separate from and in addition to the self-assessment return. A taxpayer might complete a UK property sale in June, pay CGT within 60 days (i.e., by August), and then also include the disposal on their January self-assessment return. Any additional tax due (or refund) is resolved via the annual return.

For expats selling UK residential property while non-resident: non-resident CGT (NRCGT) on UK residential property has applied since April 2015. The 60-day reporting and payment obligation applies equally to non-residents.

Commercial property and mixed-use property: different rules apply. CGT on commercial property gains by non-residents applies from April 2019. The 60-day reporting deadline also applies.

Penalties for late CGT reports: the CGT property reporting service has its own penalty regime. Late filing attracts a £100 penalty, with escalating penalties for longer delays.

Pension Contribution Deadlines

Pension contributions for a given tax year must be paid by 5 April to count for that year's tax relief. This is a hard deadline with no extension.

Key pension timing points:

• Annual allowance: £60,000 for 2025/26 (reduced for very high earners via the tapered annual allowance)
• Carry forward: unused annual allowance from the three previous years can be carried forward and used in the current year — carry forward must be calculated before making contributions
• Making pension contributions before 5 April can be particularly valuable if you expect to pay higher or additional rate tax in the current year versus next year

For expats returning to the UK mid-year: pension contributions are only available for tax years in which you are UK resident. If you return partway through the year under split-year treatment, contributions made during the UK part of the year qualify.

ISA Deadlines

The ISA allowance (£20,000 per person for 2025/26) cannot be carried forward. It is lost if unused by 5 April.

For expats: you cannot open a new ISA or contribute to an existing ISA while non-UK resident. Existing ISAs remain open and the investments can be retained (and continue to shelter income and gains from UK tax), but no new subscriptions are permitted until you become UK resident again.

Returning UK residents should prioritise maximising ISA contributions in the first year back, particularly using any available cash to fill the allowance before 5 April.

PAYE Coding Notice and P800 Reconciliation

Many individuals with UK employment or pension income receive a PAYE coding notice (Form P2) at the start of each tax year, reflecting HMRC's estimate of how much tax to deduct. The notice may include adjustments for expected investment income, benefits in kind, or underpayments from prior years.

The P800 is HMRC's year-end tax calculation, sent to employees and pension recipients where HMRC believes too much or too little tax was deducted. If a repayment is due, it is usually sent automatically within six weeks; if further tax is owed, payment is typically collected via the tax code in the following year or via self-assessment.

For expats with UK pension income and no other UK employment: the pension provider deducts PAYE tax. If the pension is the only UK income, filing self-assessment may not be required (unless other sources require it). However, if overseas income takes the total above the basic rate threshold, there may be additional UK tax due on the UK pension that needs to be settled.

Avoiding Penalties: A Practical Summary

• Register for self-assessment by 5 October after the tax year in which a new source of income arises
• File online by 31 January — HMRC does not grant automatic extensions; formal time to pay arrangements must be agreed in advance
• Pay CGT on UK property within 60 days of completion — this is a hard deadline
• Pension contributions must be in the scheme by 5 April — bank transfer timing matters for year-end contributions
• ISA deadline is 5 April — digital platforms can process subscriptions on the day, but allow margin
• Foreign income must be declared — CRS information exchange means HMRC has increasing visibility of overseas accounts

How Global Investments Can Help

Global Investments works with clients to ensure that UK tax obligations are met accurately and on time, coordinating with specialist UK tax advisers where required. For internationally mobile clients with multiple income sources, overseas assets, and pension complexity, we help structure affairs to minimise unnecessary tax exposures while remaining fully compliant. We also advise on the interaction between UK and overseas tax calendars for clients with dual residency or complex domicile positions.

This article provides general information about UK tax deadlines. Tax rules change frequently and this article reflects our understanding as of mid-2026. Always seek qualified professional tax advice based on your individual circumstances.