The fundamental thing most people get wrong about self-employment
Self-Employed Taxes UK: Employees don’t think about tax much because their employer handles it. The money arrives in their bank already processed. Self-employment is the opposite: every penny of every payment you receive is gross. Nothing’s been deducted. It’s all sitting there looking very encouraging until January comes around.
Unlike employees who have tax deducted automatically through PAYE, you are responsible for calculating and paying your own Income Tax and National Insurance through Self Assessment, keeping records of your income and expenses, and filing a return by 31 January each year. That responsibility sounds obvious, but the practical impact of setting money aside from every payment is something a lot of people start doing too late.
“Your invoice total isn’t your income. Your profit is. And your tax is calculated on that profit, not what you charged.”
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The trading allowance quick check If your gross self-employment income is £1,000 or less in a tax year, it is entirely tax-free under the trading allowance. You do not need to register for Self Assessment or tell HMRC. If you’re earning more than that, which most self-employed people are, you need to register. The deadline is 5 October the following tax year. For example, if you started being self-employed in June 2026, you’d need to register by 5 October 2027. |
What tax you actually pay: the 2026/27 rates
Self-employed people pay Income Tax and Class 4 National Insurance on their profits, both collected through Self Assessment. For 2026/27, the personal allowance is £12,570, with tax at 20%, 40% and 45%. Class 4 NIC sits alongside that at 6% on profits between £12,570 and £50,270, then 2% above.
The thing to understand is these aren’t separate calculations; you do one at a time. They run in parallel on the same profit figure. In 2026/27, a sole trader on £35,000 profit pays approximately £5,832 in combined Income Tax and National Insurance, around 17% of gross profit. That’s actually lower than many people assume going in.
2026/27 Tax Rates Self-Employed
Applied to profit (turnover minus allowable expenses)
- Personal Allowance (tax-free)——————————————————-0%
- Basic Rate Income Tax (£12,571–£50,270)————————————20%
- Higher Rate Income Tax (£50,271–£125,140)———————————40%
- Additional Rate Income Tax (above £125,140)——————————–45%
- Class 4 NIC (£12,571–£50,270)—————————————————-6%
- Class 4 NIC (above £50,270)——————————————————-2%
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Class 2 NIC: what changed Class 2 NI: the old flat weekly rate is no longer mandatory. Paying it voluntarily (£3.65/week in 2026/27) protects your State Pension entitlement if your profits are below the Small Profits Threshold. If your profits are above the threshold, Class 4 NIC automatically covers your NI record. Most self-employed people on healthy profits don’t need to pay Class 2 at all, but if you’re just starting or having a low-income year, it’s worth checking your NI position. |
Do you know what percentage of your actual profit you’re setting aside for tax each month? If the honest answer is “roughly” or “not really,” this post is for you.
Expenses where most of your actual savings live
Claiming every legitimate business expense is the single most impactful thing most self-employed people can do to reduce their tax bill. Not because expenses are a trick, but because they’re exactly what the rules say should reduce your taxable profit. The test: an expense must be wholly and exclusively for business purposes.
Here’s what most people miss: it’s not just the obvious stuff. The list of legitimate self-employed expenses is longer than most people realise, and under-claiming is genuinely common.
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Business mileage: 55p per mile (first 10,000), then 25p. Keep a mileage log. |
Home office: £6/week flat rate, or calculate actual proportion of bills. |
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Phone & internet: Business proportion only; document your usage split. |
Equipment & software: Computers, tools, subscriptions wholly for business use. |
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Training & CPD: Courses that develop existing skills (not new career routes). |
Insurance: Professional indemnity, public liability, business contents. |
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Professional memberships: Industry bodies and professional registrations relevant to your work. |
Accountancy fees: Yes, your accountant’s fees are tax-deductible. |
Example
A freelance web developer came to us in early 2025, self-employed for three years, doing well, earning around £55,000 a year. He’d been doing his own Self Assessment return, and when we asked what expenses he was claiming, the list was short: “just my laptop and some software.” That was it.
No home office claim. No mileage for client site visits. No proportion of his phone bill. No professional development. No accountancy software subscription. When we built the proper expense picture, his taxable profit dropped by just over £6,000. At his marginal rate, that was around £2,400 back in his pocket every year. He’d been leaving it on the table for three years. Over £7,000 in unclaimed refunds, gone. We filed amended returns and recovered what we could, but two of the three years had closed.
Payments on Account bill nobody saw coming.
This is the one that genuinely shocks people in their first or second year. If your tax bill tops £1,000, HMRC adds Payments on Account, which can make your first bill far larger than expected.
Here’s how it works. Your January 31 deadline isn’t just for paying last year’s tax. It’s also for paying 50% of that bill again as an advance toward this year’s tax. Then another 50% is due on 31 July. So if your first real tax bill is £4,000, you owe £4,000 for the year just passed plus £2,000 toward the current year, £6,000 total, on a deadline you may not have budgeted for at all.
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Payments on Account: the maths Tax bill for 2025/26: £4,000. Due 31 January 2027: £4,000 (balance) + £2,000 (first POA for 2026/27) = £6,000 total. Due 31 July 2027: £2,000 (second POA). If your 2026/27 profit turns out to be lower, you can apply to reduce your POA, but you need to do this actively through HMRC’s SA303 form. Don’t just pay less without telling them, or interest will run on the difference. In my experience, this is the number one cause of financial stress for self-employed people who’ve been trading for a year or two. Not the tax rate itself, the lump sum they didn’t expect. Set aside at least 25–30% of every payment you receive into a separate tax account, and this problem largely disappears. |
Key deadlines: self-employed payment calendar
5 Oct
Register for Self Assessment (if new)
5 October following the end of the first tax year you were self-employed. Miss this, and you risk a penalty, though HMRC can be reasonable if you register before filing.
31 Jan
File online return + pay tax bill + first POA.
The big one. File your Self Assessment return for the previous tax year, pay the balancing tax, and pay the first Payment on Account for the current year. All three on the same date.
31 Jul
Second Payment on Account
The second 50% POA for the current tax year. If your income is lower this year, apply to reduce it using SA303; don’t just ignore it.
6 Apr
New tax year begins, new records start.
Everything from 6 April is the new tax year. If you’re in scope for MTD from April 2027, this is when quarterly reporting starts. Keep your records clean from day one.
MTD for Income Tax does it affect you yet?
From April 2026, Making Tax Digital for Income Tax Self Assessment became mandatory for self-employed people and landlords with qualifying income above £50,000. The threshold drops to £30,000 from April 2027, bringing many more people into scope.
If you’re in scope, the annual Self Assessment return doesn’t go away, but it’s supplemented by four quarterly digital updates throughout the year, submitted through MTD-compatible software. Think of it as spreading the admin across the year rather than front-loading it all into January. HMRC has confirmed no penalties apply for late quarterly updates during the initial transition year, though the final declaration deadline carries the usual penalty regime.
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MTD scope check 2026/27 Your qualifying income for MTD is your gross self-employment turnover, not your profit, and not your take-home pay. If you invoice £52,000 but have £15,000 in expenses, your qualifying income is still £52,000. Check your gross turnover, not your profit figure, when deciding whether MTD applies to you. The threshold drops to £30,000 from April 2027. |
Estimate your own self-employed tax bill.
Put your numbers in for a rough 2026/27 estimate, including what your first January bill might look like if Payments on Account apply.
Self-Employed Tax Estimator 2026/27
Includes Income Tax, Class 4 NIC, and Payments on Account
Annual gross income (total invoiced) …………………………………………………………….45000
Total allowable business expenses………………………………………………………………..8000
£6,352 estimated annual tax
Taxable profit…………………………………………………………………………………………….£37,000
Income Tax……………………………………………………………………………………………….£4,886
Class 4 NIC………………………………………………………………………………………………£1,466
Effective rate on profit………………………………………………………………………………..17.2%
Total tax liability……………………………………………………………………….£6,352
Payments on Account apply. Your first January bill is likely to be £9,528; that’s £6,352 for the year plus £3,176 first POA toward next year. Budget for this in advance.
Uses 2026/27 rates: personal allowance £12,570; Income Tax 20%/40%; Class 4 NIC 6%/2%. England & Wales rates. Excludes pension contributions and other relief. Always get a personalised view from your accountant.
The honest verdict
Self-employed taxes aren’t complicated once you understand the structure. You’re taxed on profit. You file once a year. You set money aside throughout the year so January doesn’t hurt. You claim every legitimate expense. And you don’t wait until you’ve been trading for three years to start doing it properly.
The people who struggle with self-employed tax aren’t the ones who don’t earn enough. They’re the ones who didn’t set a tax reserve from the start, didn’t claim their full expenses, and got blindsided by estimated payments in year two. All of those are preventable problems.
The bottom line
The single most valuable thing you can do when you go self-employed is to open a separate tax account on day one and put a fixed percentage of every payment into it. 25–30% covers most people in the basic-rate band. 35–40% if you think you’ll hit the higher rate. Do that, and the January bill becomes predictable, not a crisis.
Beyond that, get your expenses right from the beginning. Don’t estimate. Don’t guess. Keep receipts, keep records, and either use an accountant or use good software that forces you to categorise properly. The cost of getting it wrong isn’t just the tax itself; it’s the amended returns, the penalties, and the three years of savings you didn’t realise you were entitled to.
At SKZ Accountants, the conversations that end with “I wish I’d done this years ago” are almost all about self-employed tax. We’d rather have that conversation when you’re just starting.
Want to make sure you’re getting this right? Talk to SKZ Accountants.
We’re specialist accountants in Ilford working with self-employed people across the UK, from sole traders just starting to established freelancers, consultants, and contractors. We handle Self Assessment filing, expense reviews, Payments on Account planning, and MTD compliance.
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