Do I Have to Do a Self Assessment Tax Return?

Of the many questions you’ll have when you first start to consider going self-employed, one unlikely to top your list is, “Do I have to complete a Self Assessment tax return?” It’s rarely the exciting part of running a business – but it is one of the most important.

Self Assessment sits at the heart of how HM Revenue & Customs (HMRC) collects tax from people whose income isn’t automatically taxed through PAYE. That includes freelancers, sole traders, landlords, company directors, and anyone earning money outside a regular salary. Get it right, and it’s a routine annual task. Get it wrong – or ignore it – and it can quickly become stressful, expensive, and time-consuming.

In this guide, we’ll break down exactly what a Self Assessment tax return is, who needs to complete one, how the rules apply in 2026, and what you can do to stay compliant without the January panic. We’ll also highlight common triggers that catch people out, practical tips to make life easier, and links to official resources so you can double-check the details when you need to.

What is a Self Assessment Tax Return?

A Self Assessment tax return (officially known as Form SA100) is how you report your income to HMRC when tax isn’t fully deducted at source. Based on the information you submit, HMRC calculates how much Income Tax and National Insurance you owe for the tax year.

Unlike employees on PAYE, where tax is taken automatically from wages, Self Assessment puts the responsibility on you to declare your income accurately and on time. This includes:

• Money earned from self-employment or freelance work
• Rental income from UK or overseas property
• Dividends, interest, or investment income above certain thresholds
• Income from side hustles, online selling, or gig-economy work
• Foreign income that isn’t taxed in the UK automatically

The tax year runs from 6 April to 5 April, and each return looks backwards at the previous tax year. For example, the 2024/25 tax year ended on 5 April 2025, and the online filing deadline is 31 January 2026.

Once you’ve submitted your return, you’ll normally need to:

• Pay any tax owed by 31 January
• Make a first payment on account for the following tax year (if applicable)
• Make a second payment on account by 31 July

HMRC provides a full overview of how Self Assessment works, including deadlines and payment options, on its official guidance page: Self Assessment tax returns – GOV.UK.

How Making Tax Digital affects Self Assessment in 2026

Self Assessment is also evolving. Making Tax Digital for Income Tax Self Assessment (MTD ITSA) is being phased in, changing how some taxpayers report their income.

From April 2026, MTD ITSA applies to sole traders and landlords with qualifying income over £50,000. Those earning over £30,000 will follow from April 2027. Under MTD ITSA, affected taxpayers will need to:

• Keep digital records using compatible software
• Submit quarterly income and expense updates to HMRC
• File an annual final declaration instead of a traditional Self Assessment return

If your income is below the MTD thresholds, the standard Self Assessment process still applies for now. However, HMRC’s direction of travel is clear: digital record-keeping and more frequent reporting are becoming the norm.

Tip: Even if MTD ITSA doesn’t apply to you yet, getting into the habit of keeping clean, digital records throughout the year can make your Self Assessment far quicker and reduce the risk of errors or missed claims.

In the next sections, we’ll look at exactly who must complete a Self Assessment tax return, common situations that trigger a filing requirement, and how to check whether HMRC expects one from you.

Do I Have to File a Self Assessment Tax Return?

As a general rule, you’ll need to complete a Self Assessment tax return if you receive income that isn’t fully taxed at source. In other words, if HMRC doesn’t already know about your income and deduct the right tax automatically, it’s usually your responsibility to declare it.

One important update to be aware of is the income threshold for higher earners. From the 2023/24 tax year onwards, the requirement to file a Self Assessment purely because you earn over £100,000 has been increased to £150,000. This means some employees with higher salaries may no longer need to file, provided they have no other untaxed income.

If you’re a sole trader, any profits you make from your business are paid to you without Income Tax or National Insurance being deducted. HMRC relies on your Self Assessment tax return to calculate what you owe, which is why filing one is a legal requirement for most self-employed people.

The same applies to self-employed individuals operating alongside other income, and to partnerships. Recent basis period reform rules mean that many businesses now need to apportion profits across two accounting periods where their year-end doesn’t align with the tax year. This makes accurate record-keeping and professional support more important than ever.

If you’re a limited company director, you’ll often need to complete a Self Assessment tax return even if you’re paid a salary through PAYE. This is because directors commonly receive dividend income, which isn’t taxed at source and must be declared separately.

Other common examples of income that usually trigger a Self Assessment requirement include:

• Rental income from UK or overseas property
• Income from abroad, even if tax has already been paid overseas
• Dividend income above the annual dividend allowance
• Interest from savings that exceeds your Personal Savings Allowance
• Income from side hustles, online selling, freelancing, or the gig economy
• Capital gains from selling assets such as property, shares, or cryptocurrency

Tip: Many people assume HMRC will tell them if they need to file a return. In reality, it’s your responsibility to check. Failing to register or submit on time can lead to penalties, even if you don’t owe any tax.

The full and up-to-date list of who needs to complete a Self Assessment tax return is available on the GOV.UK website. HMRC also provides a helpful online checker that will tell you whether you need to file a return based on your circumstances.

If you’re ever unsure, getting advice early can save a lot of stress later. At Accounting Wise, we help individuals and business owners confirm whether a return is required, register correctly, and submit everything accurately and on time.