If you sold clothes on Vinted, walked dogs at weekends, or picked up a few design jobs this year, HMRC may know about your side hustle before you tell them. Online platforms started passing seller data to HMRC in January 2025, and the deadline to register the extra income from 2025/26 is 5 October 2026. Miss it and the penalty is a percentage of the tax you owe.
TL;DR: You can earn up to £1,000 gross from a side hustle before you need to tell HMRC. Go over £1,000 and you must register for Self Assessment by 5 October following that tax year. Platforms like eBay and Airbnb now report seller data, but a report does not automatically mean you owe tax.
Do You Have to Pay Tax on a Side Hustle?
Not always. You get a £1,000 trading allowance each tax year, so if your total gross income from self-employment and casual work is £1,000 or less, you do not need to tell HMRC or pay tax on it (GOV.UK, 2026).
The word that trips people up is "gross." HMRC looks at your income before you take off costs like postage, packaging, or platform fees. Sell £1,100 of handmade candles and spend £250 on wax and jars, and you have still crossed the £1,000 line - the £1,100 is what counts, not the £850 profit.
The allowance also covers everything added together. Reselling trainers, a bit of freelance copywriting, and the odd bar shift on the side all draw on the same single £1,000, not £1,000 each. In our experience this is the point most people get wrong when they assume each hobby has its own buffer.
When Do You Need to Register for Self Assessment?
Once your gross trading income passes £1,000 in a tax year, you must register for Self Assessment by 5 October following the end of that tax year (GOV.UK, 2026). For income earned in 2025/26, that deadline is 5 October 2026.
Registration is the step that trips people up, because it comes months before the January filing date everyone remembers. It gives HMRC time to set up your record and issue a Unique Taxpayer Reference before your first return is due on 31 January 2027. If your side hustle grows past £50,000 a year, you will also be drawn into Making Tax Digital for Income Tax and quarterly updates.
There is a separate £1,000 property allowance for income from renting out a room, a driveway, or storage space, and it works the same way (GOV.UK, 2026). If you have a side hustle and a rental sideline, you get both allowances. Once you are filing, you may also need to budget for payments on account if your bill is large enough.
Is HMRC Really Watching Online Sellers?
Yes, but not in the way the headlines suggest. Since 1 January 2024, online marketplaces have been required to collect seller data, and the first reports landed with HMRC by 31 January 2025 (GOV.UK, 2026). HMRC's own guidance is blunt: a platform sharing your details "doesn't mean you necessarily owe tax or need to do anything" (GOV.UK, 2026).
A platform reports a goods seller once they pass 30 sales in a year or take more than around £1,700 (€2,000) through the site. Cross either figure and your data goes to HMRC. For services, rentals, and transport there is no floor at all, so a single booking can be reportable.
What we see most often is a Vinted or eBay user panicking over an email about data sharing when they were only clearing out a wardrobe. That is not trading, and it is not taxable. The report is a prompt for HMRC to check, not a bill.
Selling Your Own Stuff Is Not the Same as Running a Business
Clearing out personal belongings you already owned is not a taxable side hustle. Selling your old sofa, your children's outgrown clothes, or a bike you no longer ride does not count as trading, and there is nothing to declare. A single personal item only draws tax if it sells for more than £6,000, which brings Capital Gains Tax rather than income tax into play (GOV.UK, 2026).
Trading is different. If you buy or make things specifically to sell them at a profit, or you provide a service for payment on any regular basis, that is a trade. HMRC weighs the intention and the pattern: how often you sell, whether you sourced stock to resell, and whether you are chasing a profit.
One question clients always ask is where the line sits between a declutter and a business. If you bought ten pairs of trainers to flip for gain, that is trading from the first sale. If you sold ten pairs from your own cupboard, it is not.
What Is Changing With the New £3,000 Threshold?
The reporting threshold is going up, not the tax-free amount. On 11 March 2025, Exchequer Secretary James Murray announced that the Income Tax Self Assessment reporting threshold for trading income will rise from £1,000 to £3,000 gross within this Parliament, by the end of 2029 (GOV.UK, 2026).
Around 300,000 people will drop out of Self Assessment as a result, and an estimated 90,000 of them will have no tax to pay and nothing to report (GOV.UK, 2026). Those who do owe tax on income between £1,000 and £3,000 will use a new online service instead of a full return.
The trap is that the £1,000 trading allowance itself stays put (IPSE, 2026). Earn £2,500 once the change lands and you still owe tax on £1,500 - you just report it a simpler way. Until the service goes live, the £1,000 rule and Self Assessment remain the law, so nothing changes for your 2025/26 income.
The Real Cost of Not Declaring
HMRC charges a failure-to-notify penalty based on the tax you should have paid, known as potential lost revenue. The rate runs from nothing, if you have a reasonable excuse or come forward before HMRC prompts you, up to 100% of the tax where the failure was deliberate and concealed (LITRG, 2026).
Interest runs on top of any unpaid tax from the due date until you pay. The safest move is a voluntary disclosure: telling HMRC before it contacts you keeps the penalty at the low end and often at zero.
If you have already had a letter, act on it rather than ignore it. We cover the pattern in our guide to HMRC nudge letters on undeclared income, and the same principle applies here - a prompt reply beats a prompted penalty. If your bill is already overdue, our note on late payment penalties explains what accrues.
Frequently Asked Questions
Does the £1,000 trading allowance mean my first £1,000 is always tax-free?
Yes, but only up to a point. If your gross trading income for the year is £1,000 or less, it is tax-free and you do not report it. If you go over £1,000, you can either claim the £1,000 allowance as a flat deduction instead of your actual expenses, or deduct your real costs - whichever leaves you better off. You cannot do both.
I got an email from eBay or Vinted about sharing data with HMRC. Do I owe tax?
Not automatically. Platforms are legally required to report sellers who pass 30 sales or around £1,700 a year, but reaching that trigger does not create a tax bill on its own. If you were only selling unwanted personal items, there is nothing to pay. Tax only arises if you were trading - buying or making goods to sell at a profit, or providing a service for payment.
Do I still need to register if my side hustle made a loss?
Often yes. Registration is triggered by gross income over £1,000, not by profit. If your turnover crossed £1,000 but your costs wiped out the profit, you may still need to file so the loss is recorded. Registering also lets you carry a trading loss forward against future profits, which can be worth doing.
My side hustle income is between £1,000 and £3,000 - what should I do now?
For 2025/26, follow the current rules: register for Self Assessment by 5 October 2026 and file by 31 January 2027. The £3,000 reporting threshold and the simpler online service are not live yet and arrive before the end of 2029, so you cannot rely on them for this year's income.
Not sure whether your side hustle counts as trading, or whether you have crossed the £1,000 line for 2025/26? Get in touch - we work with sole traders and part-time sellers across the UK and can tell you quickly whether you need to register, what you can claim, and how to file before the 5 October deadline.