UK Tax Basics for Expats
A plain-English introduction to PAYE, National Insurance and self-assessment for anyone new to the UK tax system.
Updated 2026 · 8 min read · Written by the Relocate Relocate team
A general overview only
Your National Insurance number
A National Insurance (NI) number is a unique reference used to track your tax and National Insurance contributions, which count towards state benefits and pension entitlement. You'll need to apply for one shortly after arriving if you plan to work — your employer can usually still pay you while your application is processed.
PAYE: how most employees are taxed
Most UK employees are taxed under Pay As You Earn (PAYE), where your employer deducts Income Tax and National Insurance directly from your salary before you're paid, based on your tax code. Most employees never need to file a tax return under this system.
When you might need to file a tax return
You may need to register for self-assessment if you're self-employed, have income from property or overseas, or have more complex financial affairs — the deadline for online returns is 31 January following the end of the tax year (which runs 6 April to 5 April).
Tax residency when you move
Your UK tax residency status — and therefore what income is taxable in the UK — depends on factors like days spent in the UK and your ties to the country, assessed under the Statutory Residence Test. This is particularly relevant in your year of arrival or departure, and is worth getting professional advice on if your finances are more complex.
Frequently asked questions
Do I need a National Insurance number to work in the UK?
You'll need to apply for one shortly after starting work, though your employer can often start paying you while the application is in progress.
Will I be taxed on my worldwide income?
This depends on your UK tax residency status, which is assessed individually — we recommend speaking to a UK tax adviser, particularly in your arrival year.
What's the difference between PAYE and self-assessment?
PAYE is deducted automatically from employed salary by your employer; self-assessment is a return you file yourself, typically required for self-employment or more complex income.
Is there a double taxation risk moving from my home country?
The UK has double taxation agreements with many countries to prevent being taxed twice on the same income — a tax adviser can confirm how this applies to your situation.
More guides to help your move
UK Driving & Road Rules
Licence rules for overseas drivers, speed limits, MOT and getting on the road safely.
Housing & Renting in the UK
Deposits, tenancy types, council tax and how to avoid rental scams.
Banking for Expats
Opening a UK account before and after you land, and building credit history.
Need more than a guide?
Our relocation specialists can handle the details for you, from property to expat car leasing.
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