The UK tax system is designed to ensure that individuals and businesses pay their fair share of Income Tax. In most cases, tax is automatically deducted from wages and pensions, making the process seamless for many taxpayers.
However, there are instances where individuals and businesses must report their income and expenses themselves through a system known as Self-Assessment.
This guide will explore the critical aspects of Self-Assessment tax returns in the UK.
What is Self-Assessment Tax Return?
Self-Assessment is a system HM Revenue and Customs (HMRC) uses to collect Income Tax from those whose taxes are not automatically deducted from wages or pensions (known as PAYE). A Self-Assessment Tax Return is a form that individuals in the UK must submit to HMRC each year if they owe tax on income received.
Who Needs to File For a Self-Assessment Tax Return?
If you fall into any of these categories, you'll need to file a self-assessment tax returns:
Additionally, you may need to send a tax return if you have untaxed income, such as COVID-19 grants or support payments, rental income, tips, commission, savings and investment income, dividends, or foreign income.
How to Register For Self-Assessment?
If you're submitting a tax return for the first time, follow these steps:
It is worth remembering that this process can take up to 20 working days, so don't leave it until the last minute.
You need to supply the below information to register with HMRC:
How to Fill in a Self-Assessment Tax Return?
Self-assessment tax returns can be filed online or through the paper form.
You'll need to include details such as income, state pensions, private pensions, benefits, and other income. Be prepared with your records, including National Insurance and UTR numbers, income documentation, and any other relevant paperwork.
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When shall I file the supplementary pages while filing the Self-Assessment tax return?
You must file supplementary pages at the same time as your main Self-Assessment (SA100) tax return if you have income or circumstances that are not covered by the main form alone. These extra pages provide HMRC with the detailed information they require about specific types of income.
You must file supplementary pages if you have:
What income and expense details do you need to provide for your Self-Assessment tax return if you are self-employed?
If you are self-employed, you must report all business income and provide totals for each category of business expenses.
Business Income | Business Expenses (allowable and disallowable) |
|---|---|
Turnover | Cost of goods bought for resale or goods used |
Other business income | Construction industry - payments to subcontractors |
Cell | Wages, salaries, and other staff costs |
Cell | Car, van, and travel expenses |
Cell | Rent, rates, power, and insurance costs |
Cell | Repairs and maintenance of property and equipment |
Cell | Phone, fax, stationery, and other office costs |
Cell | Advertising |
Cell | Business entertainment costs |
Cell | Interest on bank and other loans |
Cell | Bank, credit card and other financial charges |
Cell | Accountancy, legal and other professional fees |
Cell | Other business expenses |
What income and expense details do you need to provide for your Self-Assessment tax return if you receive UK property income?
If you receive income from UK property, you must report all rental income and provide totals for all relevant property-related expenses in your Self-Assessment tax return.
Property Income | Property Expenses (allowable and disallowable) |
|---|---|
Total rent | Rent, rates, insurance and ground rents |
Other income from property | Property repairs and maintenance |
Premiums for the grant of a lease | Non-residential property finance costs |
Reverse premiums and inducements | Residential property finance costs |
Cell | Residential finance costs brought forward |
Cell | Legal, management and other professional fees |
Cell | Costs of services provided, including wages |
Cell | Travel expenses |
Cell | Other allowable property expenses |
What are the applicable tax rates for different types of income, and what are the changes to tax rates for employment, dividend, savings, and property income according to the Autumn Budget 2025?
While earned-income tax bands & tax rates remain unchanged for tax year 2024-2025 (6th April 2024 to 5th April 2025), there are significant increases to dividend, savings, and property-income tax rates, coming into effect from April 2026 and April 2027. Dividend tax increases by 2% for basic and higher-rate taxpayers from April 2026.Savings and property-income tax increases by 2% across all bands from April 2027.
1. Employment / Earned Income (Salary, Wages, Self-Employment, Pension Income)
No changes were made to the main income-tax bands for earned income. Thresholds remain frozen.
Income Type / Band | Before Autumn Budget 2025 | After Autumn Budget 2025 |
|---|---|---|
Personal Allowance | Up to £12,570 – 0% | Up to £12,570 – 0% (unchanged) |
Basic Rate | £12,571 to £50,270 – 20% | £12,571 to £50,270 – 20% (unchanged) |
Higher Rate | £50,271 to £125,140 – 40% | £50,271 to £125,140 – 40% (unchanged) |
Additional Rate | Over £125,140 – 45% | Over £125,140 – 45% (unchanged) |
--> The tax-free allowance for dividends is £500
2. Dividend Income
Rates increase from April 2026 for basic and higher-rate taxpayers. The additional rate stays the same.
Income Type / Band | Before Autumn Budget 2025 | After Autumn Budget 2025 (from April 2026) |
|---|---|---|
Basic Rate | 8.75% | 10.75% (changed) |
Higher Rate | 33.75% | 35.75% (changed) |
Additional Rate | 39.35% | 39.35% (unchanged) |
3. Savings Interest Income
Rates increase by 2 percentage points from April 2027 for individuals earning the interest income from savings.
Income Type / Band | Before Autumn Budget 2025 | After Autumn Budget 2025 (from April 2027) |
|---|---|---|
Basic Rate | 20% | 22% (changed) |
Higher Rate | 40% | 42% (changed) |
Additional Rate | 45% | 47% (changed) |
4. Property Rental Income (Individual Landlords)
Rates increase by 2 percentage points from April 2027 for individual landlords with the rental income.
Income Type / Band | Before Autumn Budget 2025 | After Autumn Budget 2025 (from April 2027) |
|---|---|---|
Basic Rate | 20% | 22% (changed) |
Higher Rate | 40% | 42% (changed) |
Additional Rate | 45% | 47% (changed) |
What are the applicable capital gain tax rates for tax year 2024/25 and 2025/26?
From 30 October 2024, the Capital Gains Tax (CGT) will be charged at the same rates for both residential property and other assets. The applicable rates for CGT will be as follows:
Band | Income Range | 2024/25 | 2024/25 | 2025/26 |
|---|---|---|---|---|
Personal Allowance | £0 to £12,570 | 18% (on property), 10% (on assets) | 18% (on property & assets) | 18% (on property & assets) |
Basic Rate | £12,571 to £50,270 | 18% (on property), 10% (on assets) | 18% (on property & assets) | 18% (on property & assets) |
Higher Rate | £50,271 to £125,140 | 24% (on property), 20% (on assets) | 24% (on property & assets) | 24% (on property & assets) |
Additional Rate | Over £125,140 | 24% (on property), 20% (on assets) | 24% (on property & assets) | 24% (on property & assets) |
The annual exempt amount (tax-free allowance) for capital gains is £3,000 for individuals. If you exceed this amount, CGT will be applied at the appropriate rates depending on the income tax band you're in.
What are the Key Deadlines For Self Assessment Tax Return?
Meeting the various deadlines is crucial to avoid penalties. Here are some key dates to remember:
Deadline for Informing HMRC
If you need to complete a tax return and have not done so before, inform HMRC by 5 October. For example, you started your self-employment on 1 June 2024, you have got until 5 October 2025 to register.
Paper Return Submission
If you submit a paper tax return, the deadline is midnight on 31 October following the end of the tax year.
Online Return Submission
For online tax returns, the deadline is midnight on 31 January following the end of the tax year.
Tax Payment Deadline
You must pay the tax you owe by midnight on 31 January. If you make advance payments, known as 'payments on account,' there is typically a second payment deadline of 31 July. Late payments may incur penalties, but you can appeal if you have a valid reason for the delay.
You can pay via
Deadline for Tax Year 2024-25
Self-Assessment Key Dates | |
|---|---|
Description | Deadline |
Registration for Self-Assessment | By 05 October 2025 |
Submission of Paper Tax Return | By 31 October 2025 |
Submission of Online Tax Return | By 31 January 2026 |
Tax Payment | By 31 January 2026 |
Amend Tax Return | By 31 January 2026 |
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Can I Amend My Return If I do not Know My Actual Profit?
In cases where you do not know your profit for the entire tax year, you should provide provisional figures when submitting your return.
Once you determine the actual profit, you have up to 12 months from the Self-Assessment deadline to adjust and file an amended tax return.
What Information is Required to Complete Your Tax Return?
Filing your tax return is a crucial annual task for individuals and businesses in the United Kingdom.
To ensure accuracy and compliance with tax regulations, you must provide specific information about your financial activities for the tax year.
Income and Gains
Your tax return should encompass all taxable income and gains for the relevant tax year. Here are the primary elements you may need to include:
Self-Employment Income and Expenses
Details of your self-employment income and expenses are essential. These will help you calculate your trading profit or loss for the year. Invoices, receipts and bank statements are required.
Property Income and Expenses
If you earn income from renting out property, you must provide information about your property income and expenses. This will enable you to determine your rental profit or loss for the year.
If you earn income from property, it's crucial to maintain the following records:
Employment and Pensions Income
Gather information about your employment and pension income, including forms like P60, P11D, and P45 from any jobs you held during the tax year
Interest Income
Ensure you have interest certificates from banks or building societies to account for the interest income you received.
Pension Contributions
Record details of any Pension Contributions made to relief at source schemes.
Capital Gains
If you made any chargeable capital gains during the tax year, you should provide information about them.
Maintaining Records
Keeping accurate records is a fundamental aspect of completing your tax return effectively. While you don't need to send original documents to HMRC (His Majesty's Revenue and Customs), it's wise to maintain these records as backup and to demonstrate that you took reasonable care when preparing your tax return.
How long shall we Retain the Records for?
The duration for which you should retain records depends on your financial circumstances:
Note
While you can maintain records in physical (paper) form, it is worth noting that HMRC is planning to introduce a digital record-keeping system for aspects such as trading and property income.
This means that you may be required to keep digital records in the future. Therefore, it's advisable to start thinking about this transition now to ensure you're well-prepared when the new system is implemented.
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How do I Register & Send the Return?
If you are required to send a tax return and have not done so before, you must register for Self-Assessment. To register, you can follow HMRC's guidelines.
If you are new to Self-Assessment, keeping detailed records and considering seeking assistance with filling in your return is essential.
What Are the Situations Where I Am No Longer Required to Send a Tax Return?
If you believe you no longer need to send a tax return, you must inform HMRC. Once HMRC agrees with your assessment, they will send a letter confirming that you are exempt from filing a return. Failing to do so before the Self-Assessment deadline of 31 January may result in penalties.
Reasons for no longer needing to send a return could include:
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What are the Penalties for Late Filing?
Failing to meet the filing and payment deadlines can lead to penalties.
Late Filing Penalties
Period of delay | Penalty |
|---|---|
One day | £100 automatic fixed penalty applies |
3 months | £10 for each following day - 90-day maximum - £900 |
6 months | Higher of - £300 or 5% of the tax due |
12 months | Higher of £300 or 5% of the tax due |
Interest is charged on late payments. You can appeal against a penalty if you have a reasonable excuse.
If you haven't filed your self-assessment tax return, you may receive a Self Assessment Penalty letter similar to the one shown below.
Sample- Self Assessment Penalty Letter
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Sample- Self Assessment Penalty Waived off for one of our client
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What are the Penalties for Late Payment of Tax?
Failure to pay the self-assessment tax by 31 January would result in the below penalties along with the interest.
Late Payment of Tax
Period of delay | Penalties |
|---|---|
30 days | 5% of the unpaid tax |
6 months | 5% of the unpaid tax (additional) |
12 months | 5% of the unpaid tax (additional) |
Example
In the tax year 2024/25 (from 6 April 2024 to 5 April 2025), if you submitted your self-assessment tax return online and had a tax liability of £15,000, the payment deadline would be 31 January 2026.
However, if you made the payment on 30 March 2026, exceeding the 30-day grace period, you would incur a late payment penalty of £750 (which is 5% of the £15,000 owed).
What Are the Penalties For Mistakes When Filing a Self-Assessment Tax Return?
HMRC has the authority to impose penalties if errors are found in your tax return; however, the severity of the penalty and whether one will be levied is contingent upon the specific nature of the mistake:
Type of Behaviour | Unprompted Disclosure | Prompted Disclosure |
|---|---|---|
Non-deliberate-within 12 months of tax being due | 0% to 30% | 10% to 30% |
Non-deliberate-12 months or more after tax was due | 10% to 30% | 20% to 30% |
Deliberate | 20% to 70% | 35% to 70% |
Deliberate and concealed | 30% to 100% | 50% to 100% |
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What is the Procedure For Changing the Tax Return?
You may need to change your tax return, such as correcting mistakes or reporting foreign income. The process for updating your return differs depending on whether you filed it online or on paper.
You must wait three days (72 hours) after filing to make changes online before updating your return. You can access your tax return within your HMRC online account, make the necessary corrections, and resubmit it.
For paper returns, you should contact HMRC to make the required amendments and send the corrected pages to the address provided. Ensure you clearly label the pages as "amendment" and include your name and Unique Taxpayer Reference (UTR).
If you need to make changes or corrections beyond the specified deadlines or for tax returns from earlier years, you should write to HMRC.
How to File Returns For Someone Who has Died?
If you are required to complete a Self-Assessment tax return for someone who has passed away, you must follow specific procedures. You will need details about the deceased person's financial affairs, including bank accounts, savings, employment or pension income, and any other sources of income.
It is essential to inform HMRC about the death using the Tell Us Once service as soon as possible. You can then post the completed tax return, adhering to the deadline provided in the letter you received from HMRC.
If you are handling the deceased's estate, you may also need to register with HMRC and submit a separate tax return on behalf of the estate.
What Are the Key Points to Consider For a Self-Assessment Tax Return?
If you fall into the above category, it is essential to understand the following key points:
Can HMRC find out about income if I don’t report it?
Yes. HMRC uses a sophisticated data-analysis system to identify undeclared income. This includes data from a wide range of sources, such as:
It’s always best to provide full and correct information and to report your income to HMRC via a self-assessment tax return.
Note
HMRC can investigate records going back 4 years for unintentional mistakes, 6 years for careless errors, and up to 20 years for deliberate tax evasion.
Do I need accounting software to file Self-Assessment Tax Returns under Making Tax Digital for ITSA?
Yes, Making Tax Digital (MTD) is the new way to do the tax returns. If you are required to comply with MTD for Income Tax Self-Assessment (ITSA), you will need to use HMRC-compatible digital accounting software.
The MTD requirements for Self-Assessment tax returns are set to roll out from 6 April 2026 for those with income over £50,000, and from 6 April 2027 for income over £30,000 with the threshold dropping to £20,000 from 6 April 2028. However, if your income is below these thresholds, you may not need to use MTD software but can continue with traditional method of filing the self-assessment tax return. The Quarterly updates combined with the annual declaration will replace the current self-assessment tax return.
MTD ITSA vs Self-Assessment Tax Return System: What Will Change for Landlords & Self-Employed?
The underlying tax rules such as income tax rates, personal allowances, deductible expenses and reliefs for self-employment and property income remain unchanged under Making Tax Digital for Income Tax Self-Assessment (MTD for ITSA).
You’ll still be required to report all taxable income (including self-employment, property and investment income) and pay income tax and Class 4 National Insurance contributions where applicable. The final declaration under MTD will continue to follow the same annual deadline (31 January following the tax year end) as the current Self-Assessment submission.
The key differences lie in how income and expenses are recorded and reported to HMRC. These differences are summarised below:
Basis of Difference | Self Assessment | MTD for ITSA |
|---|---|---|
Record-keeping | Paper, spreadsheets or any digital format as per personal convenience | Must keep digital records using MTD-compatible software like RentalBux |
Frequency of reporting | Once per year | Quarterly updates throughout the year, plus a final declaration |
Software requirement | Can use HMRC portal or paper return | Mandatory use of HMRC-recognised MTD software |
Income threshold for digital mandate | No threshold – all self-employed and landlords file annually | Over £50,000 from April 2026 and over £30,000 from April 2027 |
End-of-Year submission | Annual Self-Assessment form (SA100) | Final Declaration via software |
Visibility of tax position | Mostly visible after filing the annual return | Ongoing throughout year |
Penalties | Annual late filing penalties; interest on late payments | Points-based penalty system for missed quarterly updates; more frequent compliance checks |
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Conclusion
In summary, this comprehensive guide aims to help individuals and businesses steer the complexities of the UK Self-Assessment tax return system, ensuring compliance with tax regulations and avoiding penalties while accurately reporting their financial activities.
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