This guide is for people who have recently moved to the United Kingdom and want to know whether HM Revenue and Customs (HMRC) expects a Self Assessment tax return from them. After reading it, you will know who has to file, how to register, which deadlines the official pages set and what can happen if they are missed.
- What Self Assessment is
- Who has to send a return
- Registering with HMRC
- Filling in and sending the return
- Deadlines, payment and penalties
- FAQ
What Self Assessment is
HMRC uses Self Assessment to collect Income Tax, according to the GOV.UK guide to Self Assessment tax returns. For many people the system stays in the background, because tax is usually deducted automatically from wages and pensions. Self Assessment covers income that does not go through that automatic route. People and businesses with other income must report it in a Self Assessment tax return.
Each return covers one tax year, and the UK tax year does not match the calendar year. GOV.UK describes the 2025 to 2026 tax year as running from 6 April 2025 to 5 April 2026. You fill in a return after the tax year it covers has ended on 5 April. If you arrived part of the way through a tax year, you still deal with that April to April period. The official pages used for this guide do not explain how your arrival date or residence status affects what goes on the return.
Who has to send a return
The official guidance gives two clear triggers. The first is having income that is not taxed automatically, as wages and pensions usually are. The second is a request from HMRC. You must send a return if HMRC asks you to, whatever your other circumstances. If HMRC wrote asking for a return for the 2025 to 2026 tax year, it must be sent by the deadline stated on the letter.
For anyone unsure where they stand, GOV.UK provides a tool to check if you need to send a Self Assessment tax return for the 2025 to 2026 tax year. The tool does not send your details to HMRC, so using it does not register you or tell HMRC anything about you. The same page covers smaller sources of extra money, such as selling things online or renting out part of your home. For those, it points to a separate check on whether you need to tell HMRC.
The pages this guide draws on do not list income thresholds or every type of income that leads to a return. The checking tool works through those questions. A different rule applies to people who are already in the system. Anyone who believes they no longer need to send a return has to contact HMRC and explain why. Simply not filing does not end the obligation.
Your tax position and your immigration position are separate matters, and this guide covers only the first. If you have a question about how your visa or immigration status relates to work or income, speak to an adviser regulated by the Office of the Immigration Services Commissioner (OISC) or a solicitor regulated by the Solicitors Regulation Authority (SRA).
Registering with HMRC
Registering for Self Assessment is how you tell HMRC that it should expect a return. The deadline is 5 October, and it applies if you need to complete a tax return for the previous tax year and either of these is true:
- you have not sent a tax return before
- you registered before but did not need to send a tax return for the tax year 2024 to 2025
Someone who has never filed a UK return meets the first condition. The GOV.UK guide warns that you could be fined if you do not tell HMRC by 5 October. It does not state the amount of that fine. The main Self Assessment guide links to a separate page that explains how to register. The pages used here do not list the details asked for during registration, so check that page for the current steps.
Filling in and sending the return
To fill in a return correctly, you need records. The official guide names bank statements and receipts as examples. Keeping those documents organised through the year makes the return easier to complete once the tax year closes on 5 April.
There are two ways to send it. You can file your Self Assessment tax return online. If you need a paper form instead, you can download the SA100 tax return form or call HMRC and ask for one. GOV.UK also offers help with filling in the return, and the guide is available in Welsh (Cymraeg) as well as English.
You do not have to calculate the tax yourself. HMRC works out what you owe from the information you report, which is one more reason the figures need to be supported by records.
Deadlines, payment and penalties
For a newcomer, the dates in the official pages fall in this order. The tax year ends on 5 April. If you need to register, you must tell HMRC by 5 October. The return must be sent by the filing deadline, which the main guide links to on a separate page. The pages used here do not state that date, so check the deadlines page. If HMRC has written to you, the deadline on the letter applies. Payment of your Self Assessment bill is due by 31 January.
How much you pay depends on the Income Tax band you are in. The pages used here do not give the rates. Capital Gains Tax has a different rate, and it can apply in situations such as selling shares or a second home.
Lateness has consequences. Apart from a possible fine for not registering by 5 October, the official guide says you may have to pay interest and a penalty if you do not file and pay on time. The pages do not give amounts or explain how the penalty and interest are calculated.
FAQ
My only income is a salary taxed through my employer. Do I need to file?
The official guidance says tax is usually deducted automatically from wages. A Self Assessment return is for income outside that system, or for anyone HMRC has asked to file. The GOV.UK checking tool for the 2025 to 2026 tax year works through individual circumstances, and a letter from HMRC asking for a return means one must be sent.
What happens if I miss the 5 October registration deadline?
The GOV.UK guide says you could be fined if you do not tell HMRC by 5 October that you need to complete a return. It does not state the amount. Separately, filing or paying late can lead to interest and a penalty. The official pages used for this guide do not give figures for either.
Can I send a paper return instead of filing online?
Yes. Returns can be filed online. If you need a paper form, you can download the SA100 tax return form from GOV.UK or call HMRC and ask for one. The pages used for this guide do not state a different filing deadline for paper returns. Check the deadlines page linked from the main guide.
Does the GOV.UK checking tool share my answers with HMRC?
No. GOV.UK states that the tool will not send your details to HMRC. Using it does not register you for Self Assessment. If you need to send a return and have not filed before, you register separately, and the deadline for telling HMRC is 5 October.
Official sources: gov.uk · gov.uk
Last verified: 15 October 2026 against the official pages linked above. Rules and fees change; the official page always wins.
This is general information, not legal or immigration advice. Immigration advice in the UK may only be given by advisers regulated by the OISC or by solicitors regulated by the SRA.
Sources
- gov.uk: Self Assessment tax returns, accessed 15 October 2026
- gov.uk: Check if you need to send a Self Assessment tax return, accessed 15 October 2026 (archived copy)
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