Self-Assessment Returns: Everything You Need To Know

With the 5^th October deadline for registering for Self-Assessment fast approaching, are you prepared to file on time?

If this deadline is missed, HMRC have the right to charge you a penalty. This penalty is known as a ‘Failure to notify’ penalty and is based on the behaviour of the individual and their reason for not notifying HMRC that they should be filing a tax return.

The amount of the penalty is a percentage of the ‘potential lost revenue’, which refers to the Income Tax, Class 4 NIC and Capital Gains Tax that becomes due. The penalty can be a maximum of 100% of this amount so the sooner you tell HMRC you are required to submit a tax return, the better.

In this article, we will be taking an in-depth look at self-assessment returns and providing you with all the information you need, so that by the time that 5^th October deadline comes around, you know exactly where you stand.

The criteria for Self-Assessment Returns for 2024/25:

• You were employed as a ‘sole-trader’ and had gross earnings exceeding £1,000;
• You were a partner in a business partnership;
• Someone living in your household received Child Benefit and you had gross income for the year exceeding £60,000;
• You received foreign income (for dividends, those exceeding £500), rental income, income from an Estate or annual income from a Trust/Settlement;
• You had Capital Gains exceeding £3,000 or capital proceeds exceeding £50,000.
• If you dispose of a residential property in the tax year, this may result in a CGT Return being required to be submitted within 60 days of the disposal and you may also be required to submit a Self-Assessment Tax Return;
• You receive any other untaxed income exceeding £10,000, this includes dividends, savings, investments, tips and commission; or
• You are not a UK Resident but have UK income, including UK pensions or income from rental properties.

When do I need to file my Self-Assessment Return?

• If you opt for paper Tax Return submission, the filing deadline is 31 October 2025.
• There is, however, an exemption if you are deemed by HMRC to be unable to file online. This generally can include ministers of religion and Lloyds underwriters. In those circumstances, the deadline for a paper Tax Return submission is extended to 31 January 2026.
• Electronically filed Tax Returns have a submission deadline of 31 January 2026.

Note, there are occasions where HMRC have issued your Tax Return later than usual and they notify you of an extended deadline. This period is usually three months from the date of issue of the notice to file.

Your Tax Return for the 2024/25 tax year can be submitted at any time from 6 April 2025 and we would always recommend early completion. Amongst the various benefits of doing so, the main three are:

• Advance notice of the payment due on 31 January 2026 to enable you to plan and prepare financially for this.
• Potential reduction in the second payment on account that you may have due on 31 July 2025.
• To secure early closure of HMRC’s twelve-month enquiry window.
• Your peace of mind to know is it out of the way!

In addition to this, should your income tax liability for 2024/25 be £3,000 or less and you have income received under PAYE, you may be able to have the tax you owe for 2024/25 collected via a restriction in your tax code for the tax year commencing on 6 April 2026. This could avoid the necessity of making a lump-sum payment on 31 January 2026 and would instead allow for the amounts due to be collected in monthly instalments through your salary or pension.

Should this option seem favourable to you, your Tax Return must be submitted by 31 October 2025 if it is a paper return, or by 30 December 2025 if it is an electronically filed Tax Return.

HMRC expectations for Accuracy, Disclosure, and Legal Clarity:

While HMRC’s policy on ensuring that documents submitted to them are correct and complete has not changed, new guidelines have been developed which are aimed at people who have more complex tax affairs. In practice, you should review documents that include a declaration of correctness and completeness with care. Where there is uncertainty, these uncertainties should be disclosed, along with any novel interpretations of the law that you have made. This is to ensure transparency and openness when reporting to HMRC, especially in cases of uncertainty, which can save you from hassle down the line.

What happens if you no longer meet the criteria for Self-Assessment and HMRC has issued a notice to file?

If you receive a notice to file a tax return from HMRC and you do not meet the above criteria and therefore you do not believe that you need to complete a tax return or owe any tax, a request can be made for the tax return to be withdrawn. If HMRC agrees that you no longer require to file a tax return, they will formally write to you confirming their agreement to remove you from the Self-Assessment system.

Summary of key dates

Self-Assessment Deadlines
Registration for Self-Assessment for 2024/25	By 5 October 2025
Submission of a 2024/25 paper tax return and coding out the tax via PAYE for paper tax returns	By 31 October 2025
Tax to be collected via tax code for an online Tax Return Submission	By 30 December 2025
Submission of online tax return	By 31 January 2026
Balancing tax payment for 2024/25 and first Payment on Account for 2025/26	By 31 January 2026

If you would like any further information regarding any of the above points, or if you would like any advice or help with completing your Self-Assessment Tax Return, then please get in touch with Sarah Sargent, or your usual AAB contact.

Find out more about our Private Client Tax team. 

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