The Complete Guide to Side Hustle Tax in the UK

Last updated: 11 August 2026 · 2026/27 tax year

If you've got a day job and you're also earning money on the side, reselling, freelancing, gig work, or anything else, the tax rules around it are genuinely different from what most guides assume. This is a thorough, plain-English walkthrough of how it actually works.

In this guide
  1. Does your side hustle actually count as taxable?
  2. The £1,000 trading allowance
  3. Registering with HMRC
  4. How Income Tax really works with a job and a side hustle
  5. Class 4 National Insurance
  6. Payments on account
  7. Scotland vs England, Wales and Northern Ireland
  8. Student loan repayments
  9. Deducting expenses
  10. Selling your own belongings vs trading
  11. What happens if you don't declare it

Does your side hustle actually count as taxable?

The test HMRC actually uses isn't about how much money changes hands, it's about whether you're trading. Buying stock to resell at a profit, freelancing, offering a service, or regularly making things to sell are all trading. Simply clearing out your own wardrobe on Vinted, even for a large total, generally isn't, since you're disposing of things you already owned rather than running a business. This distinction matters more than most people realise, and it's covered in more depth in the section on selling personal items below.

The £1,000 trading allowance

Every tax year, the first £1,000 of income from self-employment or a side hustle is completely tax free, no tax, no National Insurance, and in most cases, no need to tell HMRC about it at all. This is called the trading allowance, and it applies automatically, you don't need to claim it.

Once your turnover (not profit, the total amount coming in before expenses) goes over £1,000 in a tax year, you need to register with HMRC and declare it, even if your actual profit after expenses is small. You then have a choice: deduct your real expenses from your income, or simply deduct the flat £1,000 allowance instead, whichever leaves you better off. You can't do both.

Example
If you made £1,800 reselling clothes and spent £400 on stock and postage, you could either deduct your real £400 in expenses (leaving £1,400 taxable), or deduct the flat £1,000 trading allowance instead (leaving £800 taxable). In this case, the trading allowance works out better.

Registering with HMRC

Once your side-hustle turnover goes over £1,000 in a tax year, you need to register for Self Assessment. The deadline is 5 October following the end of the tax year in which you started earning above that threshold. For example, if you crossed £1,000 at any point in the 2026/27 tax year (6 April 2026 to 5 April 2027), you'd need to register by 5 October 2027.

Once registered, you'll need to file a Self Assessment tax return by 31 January each year, covering the tax year that ended the previous April, and pay whatever you owe by that same date.

How Income Tax really works with a job and a side hustle

This is the part almost every generic tax calculator gets wrong, and it's the entire reason Sidetally exists.

Income Tax isn't calculated separately for your job and your side hustle. HMRC adds your salary and your side-hustle profit together into one combined income figure, and taxes that as a whole. Your Personal Allowance, the first £12,570 you can earn tax free each year, gets used by your salary first. If your salary already uses up all of it (which it usually does for anyone earning a typical full-time wage), then none of your side-hustle profit is tax free. It gets taxed at whatever rate applies to the top slice of your combined income, usually 20%, but 40% if your combined income pushes you into the higher-rate band.

Example
Say you earn £32,000 a year from your job, and your side hustle makes £6,000 profit. Your salary alone already uses up your full £12,570 Personal Allowance and then some, so every pound of that £6,000 gets taxed at 20%, £1,200 in Income Tax, with no tax-free slice at all. A calculator that only looked at the £6,000 in isolation would wrongly suggest a chunk of it was tax free, because it would apply a fresh Personal Allowance that, in reality, your salary has already used up.

This is why Sidetally asks for both your salary and your side-hustle profit together, rather than just the side-hustle figure on its own. It's the only way to get an honest answer.

Class 4 National Insurance

Unlike Income Tax, Class 4 National Insurance is calculated on your self-employment profit alone, not combined with your salary. For the 2026/27 tax year, you pay 6% on profit between £12,570 and £50,270, and 2% on anything above that. If your side-hustle profit is below £12,570 on its own, you won't pay any Class 4 NI on it at all, even if your combined income with your salary is much higher.

There's also Class 2 NI, which used to be a flat weekly charge for anyone self-employed. Since April 2024, most people don't need to pay it directly, profits above the Class 4 threshold get National Insurance credits automatically. It's still possible to pay Class 2 voluntarily if you want to protect your State Pension record, but this doesn't apply to most side hustlers and isn't something Sidetally's estimate includes.

Payments on account

This is the part that catches most first-time filers off guard. If your Self Assessment bill for the year comes to more than £1,000, and less than 80% of your tax was already collected at source (which it usually is, for a side hustle), HMRC will typically ask for two advance payments toward the following year's tax bill, each worth 50% of what you just owed. These are due on 31 January (alongside your actual bill) and 31 July.

Example
If your Self Assessment bill for the year comes to £1,500, your first payment on 31 January isn't just £1,500, it's £1,500 plus a £750 advance payment toward next year, £2,250 in total. A second £750 advance payment is then due by 31 July. It evens out over time, but it genuinely surprises people who aren't expecting it, budgeting for roughly 1.5x your actual tax bill in that first year is a sensible precaution.

Scotland vs England, Wales and Northern Ireland

Income Tax rates differ if you're a Scottish taxpayer, based on where you live, not where you work. Scotland uses six bands instead of three, starting at 19% and rising to 48% for the very highest earners, compared to 20%/40%/45% in the rest of the UK. At lower income levels, Scottish taxpayers often pay slightly less than the rest of the UK; at higher income levels, they typically pay more. Class 4 National Insurance is the same across the whole UK regardless of region.

Student loan repayments

If you have a student loan, it gets repaid through Self Assessment too, calculated on your combined income above your plan's repayment threshold, at 9% for undergraduate plans (Plans 1, 2, 4 and 5) or 6% for a Postgraduate Loan, and the two can stack if you have both. Like Income Tax, this is based on your total income, salary and side hustle together, not the side hustle in isolation.

Deducting expenses

If you're not using the trading allowance, you can deduct any cost that's genuinely, wholly for the business, materials, stock, postage, platform or listing fees, and a reasonable proportion of things like your phone bill if you use it for work. The golden rule is that the expense has to be for the business, not just something that happens to also help it, personal costs don't qualify just because you're self-employed.

Selling your own belongings vs trading

This trips a lot of people up, especially with platforms like Vinted, eBay, and Depop now sharing seller data with HMRC. Selling your own clothes, furniture, or other unwanted personal belongings, even for a large total, generally isn't taxable, because you're not trading, you're just disposing of things you already owned, usually for less than you originally paid. The £1,000 trading allowance and everything else in this guide only applies once you're buying or making things specifically to resell at a profit.

Platforms reporting your sales data to HMRC is just information sharing, it isn't evidence that you owe anything. The one genuine exception is a single personal item sold for more than £6,000, a valuable antique or designer item, for example, which could trigger Capital Gains Tax on the gain. Ordinary clothing essentially never reaches this threshold.

What happens if you don't declare it

HMRC increasingly receives data directly from platforms like eBay, Vinted, Airbnb, and Etsy, so undeclared trading income is more likely to be flagged than it used to be. Penalties are based on how much tax is owed and whether it looks like a genuine mistake or a deliberate omission, they scale with the situation rather than being a single fixed fine. In almost every case, registering and filing on time, even for a fairly small amount, works out far cheaper and less stressful than being investigated later.

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This guide is for general information only and doesn't constitute tax advice. Rates and thresholds reflect the 2026/27 tax year and may change. For guidance specific to your situation, speak to an accountant or HMRC directly, or see gov.uk.