Who Needs to Do Self Assessment

The 31 January Self Assessment tax return deadline might still be months away but the anxiety is real. Understanding what Self Assessment is, whether it applies to you, and what to do if you’ve fallen behind can make all the difference.

Of course, getting the right professional help from a qualified accountant makes it easier still.

What Is Self Assessment?

Self Assessment is HMRC’s system for collecting Income Tax from people whose tax isn’t automatically deducted at source through PAYE (Pay As You Earn). If you’re employed and your only income is your salary, your employer most likely handles your tax for you. That said, most people don’t realise that it is still your responsibility to make sure that you pay the right tax through your tax code. It is also your responsibility to decide whether you need to do a tax return.

The Self Assessment process involves completing a tax return each year, declaring all relevant income and gains, calculating what you owe, and paying it by the deadline. It sounds straightforward, but the rules around who needs to file, what to declare, and how to do it correctly are more involved than many people expect. Getting it wrong – or not doing it at all – can be costly. And stressful.

Who Actually Needs to Do It?

This is where confusion tends to creep in. Many people assume Self Assessment is just for the self-employed, but the net is wider than that.

You MAY need to register for Self Assessment if any of these applied to you:

• You were self-employed as a sole trader and earned more than £1,000
• You were a partner in a business partnership
• You earned more than £100,000 from any source
• You had untaxed income above £2,500 – from renting out property, freelance work, investments, or savings interest
• You received income from abroad, or lived abroad with UK income
• You were a company director receiving dividends, benefits in kind, or any income not fully taxed through PAYE – though if your only director’s income is a salary run entirely through PAYE, you may not need to file
• You or your partner received Child Benefit, and either of you earned over £60,000 which could trigger the High Income Child Benefit Charge
• You had Capital Gains from selling assets like a property, shares, or cryptocurrency above the annual exempt amount (or even below if the proceeds are over a certain amount, or you want to carry forwards a loss)

HMRC can also ask you to file a return even if none of the above apply – for instance, if they want to verify your tax affairs. And if you received a letter telling you to file, you must do so, even if you don’t think you owe anything.

If you’re unsure whether you need to file, don’t guess. A qualified tax adviser can tell you quickly and definitively – and if you do need to file, they can make sure it’s done correctly. They can also explain what to do if you don’t need to file a return because doing nothing can mean getting a fine anyway.

The Deadlines You Cannot Afford to Miss

The UK tax year runs from 6 April to 5 April the following year. After that, you have time to file and pay, but the clock starts ticking.

5 October: Deadline to register for Self Assessment if you’re filing for the first time
31 October: Deadline for paper tax returns
31 January: Deadline for online tax returns and payment of any tax owed
31 July: Second payment on account (if applicable – more on that below)

Miss the 31 January deadline and you’ll receive an automatic penalty, even if you owe no tax. Leave it three months and daily fines begin accumulating. Leave it six months and a further penalty is added – and the same again at twelve months.

It’s also worth knowing that a new penalty regime is being phased in alongside Making Tax Digital for Income Tax. From April 2026, sole traders and landlords with income over £50,000 will move to a points-based system for late filing, with a fixed penalty once a points threshold is reached, and a more graduated structure for late payment. This will extend to those with income over £30,000 from April 2027, with all Self Assessment taxpayers expected to fall under the new system by then. The direction of travel is clear: HMRC is modernising, and the expectation of timely, accurate digital compliance is only increasing.

Payments on Account: The Surprise That Catches People Out

If your Self Assessment tax bill exceeds £1,000 and less than 80% of your tax was collected at source, HMRC will ask you to make “payments on account” – advance payments towards the following year’s bill. Each payment is half your previous year’s tax bill, due in January and July.

This is often a shock. You might expect to pay £2,000 in January, only to discover you owe £3,000 – your actual bill plus the first payment on account. A good accountant will flag this well in advance and help you plan for it, rather than leaving you to find out the hard way. Another thing that catches people out is that it’s not just “income tax”, you have to pay your National Insurance through Self Assessment too so you need to factor this into the money you put to one side.

What If You Should Have Been Filing and Haven’t?

This is the part many people don’t want to think about but it’s exactly where burying your head in the sand does the most damage.

If you’ve had rental income, freelance earnings, overseas income, or any other untaxed source and haven’t been filing returns, HMRC will very likely find out. Their data-matching capabilities have grown significantly, and they routinely cross-reference information from banks, letting agents, Land Registry, and other sources including foreign tax authorities.

The good news is that coming forward voluntarily is almost always better than waiting to be found. HMRC operates a number of disclosure facilities specifically designed to help people get their affairs in order. The Let Property Campaign, for example, is aimed at landlords who haven’t declared rental income – it allows them to disclose what they owe, pay the tax due, and typically benefit from reduced penalties compared to what HMRC would impose if they opened an investigation. More broadly, a voluntary disclosure through HMRC’s online facilities can be used to report undeclared income from a wide range of sources.

We have extensive experience helping individuals navigate these processes – people who’ve been letting a property for years without realising they needed to declare it, freelancers who didn’t know their side income crossed a threshold, and others who simply fell behind and didn’t know where to start. It’s rarely as bad as people fear, and it’s always better to act than to wait. We don’t judge, **** happens. One thing you do need to know though….

Once HMRC approaches you, the window to use a voluntary disclosure closes.

Get a Professional to Handle It

For straightforward affairs, Self Assessment might be manageable. But define straightforward. Anything is easy if you know what you’re talking about. But you don’t always know what you don’t know. Prospective clients frequently tell us that their return is “simple” but this often translates to “I don’t know the rules”.

But for anything involving multiple income sources, property, overseas income, capital gains, or years of unfiled returns, the complexity – and the cost of getting it wrong – argues strongly for professional help.

A qualified tax adviser is not just typing numbers into boxes. They make sure you’re claiming everything you’re entitled to, that your return is structured correctly, that you’re not paying more than you should, and that HMRC has no grounds to come back with questions. For anyone with a disclosure to make, professional representation can make a material difference to the outcome – both in terms of how much you owe and how smoothly the process goes.

This is just one of our core “proven processes”.

Self Assessment isn’t designed to catch you out – but leaving it until the last minute, underestimating what’s required, or hoping undeclared income will go unnoticed most certainly will. If you’re not sure where you stand, or you know you need to get things in order, speak to us. The sooner you do, the better the position you’ll be in.

Get in touch with our team to discuss your Self Assessment position – whether you’re filing for the first time, need help getting up to date, or want to make a voluntary disclosure.

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