SELF ASSESSMENT
TAX RETURNS
What is a Self Assessment tax return?
Self Assessment exists to tax income that has not already been taxed.
Your PAYE salary has tax deducted before it reaches you, so that income is "taxed at source". But if you earn income from other sources that has not had tax taken off, HMRC needs to know about it. You report that income through a Self Assessment tax return, HMRC works out what you owe, and you pay the appropriate tax.
If your tax affairs are simple and everything is already taxed through PAYE, you may not need to file at all. If they are not, that is where we come in.
Do you actually need to file one?
This is the question we get asked most, and the rules have changed recently, so it is worth being clear.
There used to be an income threshold that pulled high earners into Self Assessment automatically. It was £100,000, then it rose to £150,000 for the 2023/24 tax year. From the 2024/25 tax year onwards, that income threshold has been removed entirely. If your only income is taxed through PAYE and nothing else applies, you generally no longer need to file a return simply because you are a high earner.
The catch is that plenty of other reasons to file still apply. You will usually need to complete a Self Assessment return if any of the following is true:
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You are self-employed (a sole trader) and earned more than £1,000
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You are a partner in a business partnership
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You receive rental income from property
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You have dividend or savings income above the relevant allowances
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You have capital gains to report
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You are liable for the High Income Child Benefit Charge
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You have any other untaxed income that HMRC needs to collect tax on
If you are not sure which side of the line you fall on, that is exactly the kind of thing we will check for you. Getting it wrong in either direction, filing when you should not or missing a return you needed, can lead to unnecessary admin or penalties.
Sole trader or landlord? The way you report this income is changing. From 6 April 2026, HMRC is phasing in Making Tax Digital for Income Tax (MTD IT), which replaces the single annual return with digital record-keeping and quarterly updates for qualifying businesses. We explain who is affected and when on our MTD for Income Tax page.
We do not leave it to the last minute
The UK tax year runs from 6 April to 5 April. Slightly odd dates, we know, but there is centuries of history behind them.
Once the tax year ends on 5 April, the clock starts:
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Sole traders can complete their Self Assessment as soon as they like.
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Employed clients need to wait for their annual P60 from their employer before we can finalise things.
The official deadline to file each year is 31 January. We do not work to that date. We aim to have every client's Self Assessment filed by 31 October, three full months ahead of the deadline.
That means no January scramble, no nasty surprises, and plenty of time to plan for any tax due rather than finding out about it days before it is payable.
Are you ready to work with accountants who file months before the deadline, not minutes before it?
Why clients choose Sadler Advisory
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Early, every time. Filed by 31 October, not 31 January.
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Accurate and compliant. ICAEW-regulated, with your full position reviewed properly.
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Clear on what you owe. You know your tax bill well in advance, so you can plan for it.
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Joined up with everything else. From bookkeeping to MTD for Income Tax, we keep the whole picture connected.
