A Self Assessment tax return is required from anyone whose income is not fully taxed through PAYE: the self-employed, partners, landlords, people with foreign income or capital gains, and new UK residents who want to use the FIG regime. The online return for the 2025/26 tax year is due by 31 January 2027, and any tax owed must be paid by the same date. This guide sets out the current HMRC rules, deadlines, penalties and the changes that took effect in 2025 and 2026.
What is a Self Assessment tax return
Self Assessment is the system HM Revenue and Customs (HMRC) uses to collect Income Tax and Capital Gains Tax on income that has not passed through the PAYE (Pay As You Earn) payroll system. If you are employed and have no other income, your employer deducts tax for you. As soon as you receive rent, dividends, interest, business profits, gains from selling assets or money from abroad, HMRC expects you to work out the tax yourself and report it.
The UK tax year runs from 6 April to 5 April of the following year, and a return always covers a tax year that has already ended: in autumn 2026, returns are being prepared for 6 April 2025 to 5 April 2026. Income Tax for 2026/27 is charged on a progressive scale: the standard Personal Allowance is £12,570, the basic rate is 20%, the higher rate of 40% applies above £50,270 and the additional rate of 45% above £125,140. Your Personal Allowance goes down by £1 for every £2 of adjusted net income above £100,000. Scotland has its own rates and bands, and the current figures are published on the GOV.UK Income Tax rates page.
A tax return is also a tool, not only an obligation. Many reliefs and special regimes, including the exemption of foreign income under the FIG regime and credit for tax already paid in another country, only apply if you claim them in your return. If no return is filed, the relief is simply not given.
Who needs to send a Self Assessment tax return in the UK
- Self-employment income above £1,000 before deducting expenses
- Membership of a UK business partnership as a partner
- Capital gains on which Capital Gains Tax is due
- High Income Child Benefit Charge not paid through PAYE
- Rental income from UK property, including for non-residents
- Foreign income and gains received by UK tax residents
- Claims for the FIG regime and reliefs available only in a return
- A notice from HMRC asking you to file for a particular tax year
GOV.UK lists the first four as mandatory: if in the last tax year you were self-employed and earned more than £1,000, were a partner in a business partnership, had to pay Capital Gains Tax, or had to pay the High Income Child Benefit Charge (HICBC) and do not pay it through PAYE, you must send a return. HICBC applies once individual income is over £60,000, and at £80,000 or more the whole of the Child Benefit is repaid. For untaxed income such as rent, tips, commission, savings interest, dividends and foreign income, HMRC looks at your circumstances, and a return is often needed as well. The full list is on the GOV.UK “Who must send a tax return” page.
When a return is usually not needed
If all your income comes from wages or a pension taxed in full through PAYE and you have no other sources, you normally do not need to file unless HMRC writes to you and asks for a return. A separate high-earner threshold that used to trigger a return automatically no longer appears in the current GOV.UK list. A high salary on its own is not the issue: foreign accounts, investments or letting out property almost always change the picture.
If you are not sure whether you are UK resident for tax purposes, start by checking your status with the UK tax residence test. Your status decides whether you report UK income only or your worldwide income.
Benefits of seeking tax return support from Imperial & Legal
- Assessment of your UK tax residence under the STR before any calculation
- Review of FIG regime eligibility and its real value in your case
- Selection of every supplementary page you need: SA105, SA106, SA108, SA109
- Credit for tax paid abroad through Foreign Tax Credit Relief
- Tracking of registration, filing and payment on account deadlines
- Preparation for Making Tax Digital for landlords and sole traders
- Support with HMRC correspondence and penalty appeals
Even when the grounds for filing are clear, the dates matter most in practice: a missed registration or a late payment triggers penalties automatically, and they grow month by month.
Self Assessment deadlines for the 2025/26 tax year
For the 2025/26 tax year (6 April 2025 to 5 April 2026), HMRC has set the dates below. If you are filing for the first time, or did not send a return last year, you need to register for Self Assessment by 5 October 2026 first. All dates are published on the GOV.UK “Self Assessment tax returns: deadlines” page.
| What you need to do | Deadline |
|---|---|
| Tell HMRC you need to send a return (registration) | 5 October 2026 |
| Send a paper SA100 return | 31 October 2026, 11:59pm |
| File online if you want to pay through your PAYE tax code | 30 December 2026, 11:59pm |
| File your online return | 31 January 2027, 11:59pm |
| Pay tax for 2025/26 and the first payment on account for 2026/27 | 31 January 2027, 11:59pm |
| Pay the second payment on account for 2026/27 | 31 July 2027, 11:59pm |
Payments on account are advance payments towards next year’s bill. Each of the two payments is half of the tax you owed last year. You do not have to make them if last year’s bill was less than £1,000 or if more than 80% of the tax you owed was already paid outside Self Assessment, for example through PAYE. If you know your income will be lower this year, you can ask HMRC to reduce them online or with form SA303, but if the final bill turns out higher, HMRC charges interest on the difference. The balancing payment is due by 31 January and includes any Capital Gains Tax and student loan repayments. See the GOV.UK guidance on payments on account.
Late filing and late payment penalties and HMRC interest
Penalties for filing late and for paying late are charged separately and add up. Even when the tax due is small, the fixed penalties for a late return can easily exceed it. The amounts under the standard Self Assessment rules are set out on the GOV.UK “Self Assessment tax returns: penalties” page.
| What happens | Consequence |
|---|---|
| Return filed after the deadline | £100 penalty |
| Return more than 3 months late | £10 a day, up to £900 |
| Return more than 6 months late | A further 5% of the tax due or £300, whichever is greater |
| Return more than 12 months late | Another 5% or £300, whichever is greater |
| Tax not paid on time | 5% of the unpaid tax at 30 days, 6 months and 12 months |
| Any unpaid tax | Interest at the Bank of England base rate plus 4% (from 6 April 2025) |
If you already use Making Tax Digital, a new system applies from the tax year you join: each late submission earns a point, and reaching 4 points triggers a £200 penalty; for late payment, 3% is charged after 15 days, another 3% after 30 days and then 10% a year. You can usually appeal a penalty within 30 days of the date it was issued if you have a reasonable excuse, and HMRC publishes examples on the GOV.UK “Reasonable excuses” page.
How to file a Self Assessment tax return: five stages
Preparing a return starts long before the form is filled in. First your tax status and income sources are identified, then documents are gathered, regimes and reliefs are chosen, and only then is the tax calculated. Below is a typical sequence for a client with income in more than one country.
Review of tax residence and income sources
HMRC registration and documents for the year
Tax calculation and choice of reliefs
Preparing, approving and filing the return
Payment, payments on account and next year
Each stage can be completed on your own through your HMRC online account, but in practice most errors happen at the third stage, when regimes are chosen and foreign tax credit is calculated. That is where the final tax bill is really decided.
Tax support
Self Assessment tax return, start to finish
Status and risk review
Residence under the STR, income sources and FIG regime eligibility
HMRC registration
Registration, your UTR and access to your HMRC online account
Calculation and planning
Scenario comparison, reliefs and credit for tax paid abroad
Filing and deadlines
Filing the return, payments on account and HMRC letters
Situations where you live outside the UK but earn income here, or have recently arrived and hold assets in other countries, need particular attention.
Self Assessment tax return for non-UK residents
Being non-resident does not remove UK tax on UK income. Non-residents usually pay tax on income they receive in the UK, but not on foreign income. According to GOV.UK, you usually need to send a return if you live abroad and rent out property in the UK, work for yourself in the UK or have taxable interest from UK banks or building societies. The detail is on the GOV.UK “Tax on your UK income if you live abroad” page.
A typical case for Imperial & Legal clients is a London flat let out after the owner has moved to another country. The rental income goes on the SA105 pages, and non-resident status is confirmed on the SA109 pages. A non-resident is not always entitled to the Personal Allowance, so eligibility has to be checked separately against the conditions published on GOV.UK. If you are eligible, you pay tax only on income above the allowance; if not, you pay tax on all of it.
Residence is decided by the Statutory Residence Test (STR). You are automatically UK resident if you spend 183 days or more in the UK in the tax year. Other automatic tests look at whether your only home is in the UK or whether you work full time here, and the sufficient ties test covers cases in between. Residents pay UK tax on worldwide income, non-residents only on UK income. The rules are summarised on the GOV.UK tax residence page. Your status can change from one year to the next, so it needs checking again for every return.
The FIG regime replaces the remittance basis from April 2025
From 6 April 2025, the remittance basis for non-domiciled residents has been abolished. The £30,000 and £60,000 remittance basis charges that still appear in many articles no longer apply. Instead of domicile, the system now looks at how many years you have been UK resident, and the remittance basis has been replaced by the 4-year foreign income and gains (FIG) regime. A detailed analysis of the reform is available in the article “Non-dom status abolished: what changed and what to do now”.
The FIG regime is available to UK tax residents in their first 4 years of residence, provided they were not UK resident for at least 10 consecutive years before that. The key rules are:
- the regime is claimed only in a Self Assessment return, separately for each tax year;
- qualifying foreign income and gains are exempt from UK tax, even if the money is brought to the UK;
- making a claim means losing the tax-free allowances for Income Tax and Capital Gains Tax;
- exempt foreign income still counts towards adjusted net income, which affects HICBC and eligibility for help with childcare costs.
For people who used the remittance basis in the past, the Temporary Repatriation Facility (TRF) is available: foreign income and gains that arose before 6 April 2025 can be designated at a reduced rate of 12% in 2025/26 and 2026/27 and 15% in 2027/28. The election is made on the SA109 pages. The conditions for the regime are published on the GOV.UK “Check if you can claim the 4-year foreign income and gains regime” page.
If you are choosing where to relocate and comparing regimes for new residents, it helps to look at the alternatives: the article “UK FIG regime vs Italy, Cyprus and Portugal” compares the duration, cost and limits of each option.
Making Tax Digital: what changes for landlords and sole traders
From 6 April 2026, Making Tax Digital for Income Tax (MTD) became mandatory for sole traders and landlords whose qualifying income, meaning gross self-employment and property income before expenses, was above £50,000 on their 2024/25 return. From 6 April 2027 the threshold falls to £30,000, based on the 2025/26 return, and from 6 April 2028 to £20,000. You can check whether it applies to you on the GOV.UK “Find out if and when you need to use Making Tax Digital for Income Tax” page.
MTD does not replace the annual return; it adds quarterly reporting on top of it. Participants keep digital records in compatible software and send quarterly updates of their income and expenses. For the first year, the deadlines are 7 August 2026, 7 November 2026, 7 February 2027 and 7 May 2027. The tax return and payment are still due by 31 January.
| Feature | Standard Self Assessment | Making Tax Digital for Income Tax |
|---|---|---|
| Who it applies to | Everyone who has to send a return | Sole traders and landlords with qualifying income above the threshold |
| Record keeping | Any format | Digital records in compatible software |
| Reporting during the year | Not required | Quarterly updates, 4 times a year |
| Annual tax return | By 31 January | By 31 January |
| Late submission penalties | £100, then daily and percentage penalties | Points-based system, £200 penalty at 4 points |
If your rental and business income is close to £30,000, it is worth checking your 2025/26 figures early: HMRC will use that return to decide whether you need to join MTD from April 2027. Exemptions exist for some groups; some apply automatically, while others need an application.
Practical examples: which return is needed in different situations
The examples below are illustrative. They show how the same rules work differently depending on residence status and the mix of income. The figures and conclusions are for illustration only and do not replace an individual calculation.
New resident with foreign dividends
An entrepreneur moved to London in 2025, had not been UK resident for more than 10 years before that, and receives dividends from a company in another country. They can claim the FIG regime and pay no UK tax on qualifying foreign dividends, but lose the Personal Allowance. If their UK salary is high, the FIG claim usually comes out ahead; if the foreign income is small, it may not. Either way, the regime can only be claimed through a return with the SA109 pages completed.
Non-resident with a London flat to let
A family moved from the UK to the UAE and let out their London flat. Under the STR they are now non-resident, but the rental income is still UK income and is taxed in the UK. They need a return with the SA105 and SA109 pages, and allowable costs such as management, repairs and insurance reduce the taxable amount. If the gross rent is approaching the MTD threshold, it is worth checking early whether quarterly reporting will be needed.
Employee with investment income abroad
A specialist works in London on a Skilled Worker visa, and tax on the salary is deducted through PAYE. They have a brokerage account in another country, where they sold shares at a gain and received interest. This income does not go through PAYE, so a return with the SA106 and SA108 pages is needed, and tax withheld abroad can be credited through Foreign Tax Credit Relief within the limits set by the relevant double taxation agreement.
Real client situations are usually more complex: income in several countries, a change of status in the middle of the year, family assets. Below are stories of Imperial & Legal clients who went through tax return preparation and tax planning.
Client stories about UK tax returns
UK tax return for a spouse visa holder
Paola and James are an international couple. She's originally from Brazil. And he is Irish, but now living in London. They share a common sphere of activity - they both work as engineers in the...
English tax return for a client with an Innovator visa
Santiago came to the UK from Costa Rica. We knew him from when he applied for his Innovator's visa to the UK. Imperial & Legal helped him to put together the necessary documents and...
Tax Returns for Client Who Applies for Indefinite Leave to Remain
Anna relocated to the United Kingdom from New Zealand. She had been happy there with her husband Frederik. He had had a successful automobile business....
Tax planning for married couple relocating to UK
Madina and Yuri are a married couple from Kazakhstan. They relocated to the United Kingdom a year ago when Yuri was invited to join a project to develop educational computer games. He agreed right...
Tax planning for a foreign person when moving and buying a property in England
Pablo is originally from South America. He has been living in Britain for several years. His business involves supplying construction equipment to...
Tax planning for married couple moving to England to settle (Indefinite Leave to Remain)
Tobias and Hannah moved to the UK from Austria. The couple received a pre-settled status, which is granted to EU citizens, permitting them to relocate...
One client who moved to London with an online business and payments from several countries explained why she decided not to deal with UK tax on her own.
When my husband got an interesting job offer from the UK, we immediately decided to relocate. I run an online business and can work from anywhere in the world. However, I understood that it was not so easy since I received payments from different countries and feared that I might get into trouble with tax authorities. That’s why, I decided to contact Imperial & Legal’s specialists who helped me do everything right.
As in Madina’s story, the most common problems arise not because the rules are complicated, but because an income source was left out of the return or reported on the wrong page.
Common mistakes when preparing a tax return
Most mistakes repeat year after year. Some lead to overpaying tax, others to extra tax, interest and penalties. Check your situation against this list before filing:
- Getting residence status wrong. Status is decided by the STR for each tax year, not by your visa or where your family is registered.
- Leaving out foreign income. Residents report worldwide income: interest, coupons, dividends and gains on assets sold abroad.
- Claiming FIG without a calculation. The regime removes the Personal Allowance and is not always worth it, so the decision should be based on figures.
- Not claiming foreign tax credit. Foreign Tax Credit Relief has to be claimed in the return, otherwise the same income may be taxed twice.
- Forgetting payments on account. The first payment on account is due on 31 January together with the tax, so in the first year the bill can be around one and a half times what you expected.
- Registering at the last minute. You cannot file without a UTR, and the registration deadline is 5 October.
- Missing rental expenses. Allowable management, repair and insurance costs reduce your tax, but only if they are documented and reported correctly.
If a mistake has been made, the return can be corrected. An online return can be amended within 12 months of the filing deadline, so corrections for 2024/25 are accepted until 31 January 2027. After that, you need to write to HMRC, and an overpayment relief claim can be made up to 4 years after the end of the tax year it relates to. The rules are on the GOV.UK “Corrections” page.
To make the consultation and the preparation itself quicker, it helps to know in advance which documents you will need and which pages of the return apply to you.
Documents and supplementary pages you will need
The main return is the SA100. Depending on your income, supplementary pages are added to it. When you file online, the system offers the right sections if you answer the opening questions correctly, but for a paper return or commercial software you need to choose them yourself. The full list of forms is on the GOV.UK “Self Assessment tax return forms” page.
| Page | What it is for |
|---|---|
| SA102 | Employment income, including company directors |
| SA103S / SA103F | Self-employment, short and full versions |
| SA104S / SA104F | Partnership share |
| SA105 | UK property income |
| SA106 | Foreign income or gains and foreign tax credit |
| SA108 | Capital gains |
| SA109 | Residence, the FIG regime and the TRF |
Before the return is prepared, gather:
- your P60 from your employer and P11D if you have taxable benefits;
- statements for bank and brokerage accounts in the UK and abroad;
- tenancy agreements, agent statements and evidence of property costs;
- purchase and sale documents for assets, to calculate capital gains;
- evidence of tax paid in other countries;
- your dates of arrival in and departure from the UK during the tax year, for the STR.
Documents need to be kept after filing as well. The self-employed must keep records for at least 5 years after the 31 January submission deadline for the relevant tax year, as set out in the GOV.UK guidance on how long to keep records. For UK business bookkeeping, see accounting services from Imperial & Legal.
Self Assessment in 2026: the key points
In the last two years the rules for international residents in the UK have changed more than in the previous decade: the remittance basis has been replaced by the FIG regime, interest on unpaid tax has gone up, and landlords and sole traders now report quarterly. The Self Assessment return remains the central document through which almost every relief is claimed and through which HMRC assesses what you owe. For a wider overview of the tax system, see UK taxes and international tax planning.
Key takeaways
- The 2025/26 online return is due by 31 January 2027, and first-time filers must register by 5 October 2026.
- Payments on account are half of last year’s tax, paid twice a year on 31 January and 31 July.
- The remittance basis ended on 6 April 2025, and the FIG regime can only be claimed in a return.
- Non-residents file returns for UK income, such as rent from UK property.
- MTD is mandatory from April 2026 for qualifying income above £50,000, and from April 2027 above £30,000.
- A mistake in an online return can be corrected within 12 months of the filing deadline.
The information on this page is general in nature, reflects HMRC rules at the date of publication and is not individual tax advice. The tax consequences depend on your circumstances, so professional advice is recommended before making any decisions.
