Do You Need to Complete a Self-Assessment Tax Return?

Understanding the evolving UK tax system can feel overwhelming and challenging. For new business owners or those moving from full-time employment to self-employment, a term which you may have heard but never needed to explore until now is the Self-Assessment tax return. Depending on your plans, you may need to complete a form.

For many taxpayers, income tax is already calculated and deducted at source through Pay As You Earn (PAYE), meaning no additional action is required. However, if your financial situation is more complex, you may have obligations beyond the standard PAYE system.

At Hamlyns, we regularly help business professionals understand their tax responsibilities, available allowances and reliefs, and ensure they remain compliant with HMRC by meeting all required deadlines. In this article, we’ll clarify who needs to file a Self-Assessment return form, highlight common scenarios, and explain the risks of missing important deadlines.

Who Needs to Complete a Self-Assessment?

Not every taxpayer needs to complete their own Self-Assessment tax form. For instance, if your income is fully taxed through PAYE (such as a standard full-time employment salary), you will not need to file one.

However, if you have received income that hasn’t been taxed at source, or your financial affairs and responsibilities extend beyond standard employment, HMRC may ask to you file and submit a SA tax return.

You’ll generally need to complete a Self-Assessment if you:

• Are self-employed: If you received gross income of more than £1,000 from self-employment during the current tax year, you must register for Self-Assessment.
• Earn rental income: Landlords who earn more than £1,000 from property rental must notify HMRC. If your rental profit exceeds £2,500, you’ll need to register for Self-Assessment. There are some exceptions through the Rent a Room scheme, however.
• Have overseas taxable income: Income from overseas sources, such as employment, pensions, savings, investments, or property, must be reported to HMRC and typically requires a separate Self-Assessment return.
• Work as a partner in a business: If you’re a business partner receiving a share of partnership profits, you’ll need to file a tax return.
• Receive Child Benefit with higher income: If you or your partner claim Child Benefit and either of your individual incomes exceeds £60,000 (increased from £50,000 in 2024), you’ll need to complete a return and may face the an additional high income charge.
• Have substantial savings or investment income: If your savings income exceeds your Personal Savings Allowance (£1,000 for basic rate taxpayers, £500 for higher rate taxpayers) or your investment income exceeds £500, you must notify HMRC. If combined income from savings and investments exceeds £10,000, Self-Assessment registration is required.
• Are an off-payroll worker or contractor: Those providing services through an intermediary will generally need to file a Self-Assessment.
• Have significant capital gains: If you’ve disposed of assets and made gains exceeding the annual exempt amount (£3,000 for the 2025/26 tax year), you must report this to HMRC. This will also be subject to Capital Gains Tax (CGT).
• Want to claim substantial employment expenses: Employees seeking tax relief on expenses exceeding £2,500 per year will need to file a return.

It’s also worth noting that even if none of these situations apply to you, if HMRC has sent you a notification stating you need to complete a Self-Assessment, you must do so. You can query this directly with them, or request that your business accountant do this on your behalf.

Key Self-Assessment Tax Return Deadlines

Self-Assessment operates on strict deadlines, and missing them can result in automatic penalties:

• 5th October: Deadline to notify HMRC if you have new income that needs to be reported and you weren’t previously registered for Self-Assessment.
• 31st October: Paper tax return submission deadline
• 31st January: Online tax return submission deadline and payment deadline for any tax owed

If you’re late filing your tax return, you could be subject to a penalty, with additional charges accumulating depending on the extent of the delay, and any unpaid tax from the deadline could be subject to interest on top of it. Therefore, paying close attention to deadlines is vital.

For more information, refer to our guide on what happens if you fail to declare income to HMRC.

Why Consider Partnering With Hamlyns for Accounting Support?

At Hamlyns, we understand that tax obligations can often be confusing for new self-employed professionals or those who have never submitted a Self-Assessment before, particularly when your financial circumstances change.

Our experienced chartered accountants take the complexity out of Self-Assessment returns filing, ensuring your returns are accurate, submitted on time, and reflective of your personal circumstances.

Whether you’re newly self-employed, have recently started earning rental income, or simply want peace of mind that your tax affairs are in order, we’re here to provide expert guidance and professional, proactive support. Contact Hamlyns today to discuss how we can help you stay on top of your Self-Assessment obligations, and support your business growth in ways from budgeting and target setting to long-term succession planning, and everything in between.