Do I need to complete a tax return? A UK checklist for 2026/27

Tom Biggs ACA CTA explains the scenarios for exactly when you need to think about filing a tax return and what to consider.

As a firm of accountants and advisors, some of the most common questions we hear from new clients are:

• 'Do I need to complete a tax return?'
• 'Does this actually apply to me?' 
• 'What happens if I should've filed a return, but didn't?'

If you're asking yourself these questions then you're not alone. 

It's common to many business owners, freelancers, and individuals. 

The honest answer is that not everyone does but if you should and you then don't, that will cause you financial headache's and problems. 

That's why we've produced this blog post, so that you don't have to rely on guesswork and can instead reference this tax return checklist to provide you with a clear indicator as to what you need to do. 

Quick links to sections covered in this blog post include:

1. What is a Self Assessment Tax Return? (A simple explanation)

A Self Assessment Tax Return is what you use to tell HM Revenue & Customs (HMRC) about any of your income that hasn't already been taxed automatically. In simple terms this means if HMRC doesn't already know about your income through Pay As You Earn (PAYE) then you'll usually need to report it yourself. 

Examples of this can include:

• Self-employment income
• Rental income
• Dividends
• Bank interest
• Investment or foreign income

2. Quick checklist: Do any of these apply to you? 

If you tick any of the below boxes, then there's a strong chance that you'll need to complete a Self Assessment Tax Return. 

a) You're self employed (even part-time)

If you earn more than £1,000 from self-employment, you'll usually need to file a tax return. 

This is particularly relevant to:

• Influencers
• Freelancers
• Sole traders
• Side hustles that generate additional income streams

The above applies even if it's not your main source of income. 

b) You're a company director

If you run a limited company, you'll often need to complete a tax return and this is the case especially if you're taking:

• Dividends
• A combination of dividends and salary

c) You have untaxed income

This is a scenario that often catches people out. It's important you understand and remember this, if HMRC haven't already taxed your income, then it's your responsibility to declare it!

Examples of that income can include:

• Interest generated from savings
• Rental income from property
• Dividends
• Foreign income

If tax hasn't been deducted then the onus is on you to report it.

d) You've sold assets 

If you've sold assets and made a gain then you'll need to report this for Capital Gains Tax. A gain refers to the profit made when you sell, gift, or exchange an asset for more than you paid for it. The increase in value is taxed. Assets can include:

• A second property (you'll also have to file a CGT 60-day return)
• Shares and investments

e) HMRC requests one

If you receive a notification from HMRC to complete a return then you must do it. It has to happen even if you don't think you owe anything. 

3. Scenarios where you might not need to complete a tax return

You may not need to file if:

• All your income is taxed through PAYE
• You don't have any additional income streams
• HMRC hasn't contacted you to file a return

Just be warned, mistakes can easily happen based on assumption that you're covered, when actually you're not!

4. A reality check

As mentioned earlier, most personal tax issues don't come from people deliberately ignoring matters. They come from people assuming, and not fully comprehending tax legislation in relation to their personal finances: 

'I didn't realise this applied to me'. 

Examples of this can include:

• Starting a side hustle this year
• Extracting dividends for the first time
• Renting out a property
• Enjoying a particularly strong financial year

So, if this sounds familiar then review this post, consult a tax professional if you're not sure, but above all else, don't just assume you don't need to file a tax return. 

5. What happens if you should file, but don't?

Unfortunately many people don't consider this until it's too late. If you fail to complete a tax return when required then:

• You may receive an automatic £100 penalty
• More penalties can build up over time
• Interest can be applied to any unpaid tax amount
• HMRC may also open an enquiry into your financial affairs

Furthermore HMRC increasingly has access to more data than people may care to realise. Don't therefore rely on hoping you won't be picked up would be our advice. 

Can I just ignore this?

In short, no. 

If you're likely to need to be filing then ignoring it can lead to:

• Automatic penalties
• Increasing fines
• The stress of dealing with HMRC to then file a return subsequently

6. When do you need to register?

If you need to complete a tax return then you usually have to register by 5 October following the end of the tax year in which you made your income. 

Don't leave it too late, this delays the whole process and can leave you at risk of penalties. 

7. A simple way to think about it

If you're still unsure if you need to fill in a tax return then consider if the following apply to you:

• You earn money outside of PAYE
• You have multiple sources of income
• Your financial situation has changed significantly this year

Here's the thing, by the time you get to January:

• The deadline is close meaning there's not much time to prepare and file
• Pressure then likely increases
• Mistakes become more likely to occur

8. Getting clarity through professional advice

You may have ticked one of the bullet points from above. So, now you know a tax return may be needed, but you aren't totally sure as to why. It's sensible to pause and ask this question, better to double check than get things wrong. 

That's why we recommend a quick conversation with us which can:

• Confirm if you really do need to file a return
• Help you plan ahead and budget
• Provide you with peace of mind as to what needs to be reported
• Ensure you don't fall foul of late filings, missed payments, and penalties

9. What to do next?

If you think, or you've confirmed, that you need to file a tax return, the next step is to understand:

• How the process works
• The information you'll need to supply
• The deadlines you need to plan around

Here is a link to the tax return page and aide memoire we supply to our clients shortly after the beginning of the new tax year. Whilst considerable, it's an indicative but not exhaustive list of the kinds of items relevant to this process.    

10. A tax return summary

So remember, you'll likely need to register and complete a tax return if you:

• Are self-employed
• Receive any untaxed income
• Are a company director
• Have received a request to file by HMRC

If none of the above is applicable, you may not need to apply but it's most likely worth checking in with us to make sure. 

The content of this post was created on 11/05/2026.

Please be aware that information provided by this blog is subject to regular legal and regulatory change. We recommend that you do not take any information held within our website or guides (eBooks) as a definitive guide to the law on the relevant matter being discussed. We suggest your course of action should be to seek legal or professional advice where necessary rather than relying on the content supplied by the author(s) of this blog.