If you sold a few hundred pounds of unwanted clothes online last year, you almost certainly owe HMRC nothing — but you may still hear from it, because the rules on what online platforms report changed, and a quiet sales letter is not the same as a tax demand. With the summer break giving side-hustlers time to look at their accounts, this is a good moment to understand where the genuine tax line sits, what the platforms now tell HMRC, and what records actually protect you.
The confusion is understandable. Headlines about "the side-hustle tax" did real damage, leaving casual sellers convinced they'd be taxed on clearing out a wardrobe. That's not how it works — but the reporting underneath has changed, so it pays to know the facts rather than the panic.
The £1,000 trading allowance is the line that matters
Every UK individual gets a trading allowance of £1,000 of gross income per tax year, separate from any salary. Earn up to £1,000 from a side activity — selling crafts, freelance bits, dog-walking, reselling for profit — and you have nothing to declare and no tax to pay on it. Cross £1,000 in gross income (not profit, gross), and you're into self-assessment territory and need to register with HMRC.
Two distinctions trip people up. First, this is about trading — buying or making things to sell at a profit, or providing services. Selling your own used possessions for less than you paid is not trading and doesn't count at all; that wardrobe clear-out is genuinely tax-free no matter the total. Second, the £1,000 is gross income across all your side activities combined, not per platform. Three hundred pounds on one marketplace plus eight hundred on another is £1,100 gross — over the line, even though neither platform alone looks like much.
What the platforms now report — and what that letter means
Under rules that took effect for digital platforms, sites like online marketplaces, accommodation-letting apps and gig-work platforms now report seller information to HMRC each year. The trigger for reporting is broadly set at around 30 sales or roughly €2,000 (about £1,700) of proceeds in a year, so a genuinely casual seller below that may not be reported at all.
Crucially, being reported is not the same as owing tax. HMRC receiving your sales data simply means it can cross-check declarations. If you sold used personal items, you owe nothing and the data confirms it. If you were trading and didn't declare, the data is how HMRC finds out. The letters some sellers received are nudge letters — prompts to check your position, not bills. Ignoring one when you genuinely should have declared is the mistake; panicking over one when you only sold old furniture is wasted worry.
The records that actually save you
Whether you're under the allowance or comfortably over it, the same simple habit protects you: keep evidence. For a casual seller, that means being able to show the items were your own used belongings — original purchase receipts, photos, anything that demonstrates you sold for less than you paid. For an actual side business, it means a basic record of income and expenses, kept as you go rather than reconstructed in a panic the following January.
- Log every payment in as it arrives — date, amount, what it was for.
- Keep receipts for anything you buy that the activity needs — materials, postage, the proportion of your phone bill that's genuinely business.
- Hold on to the records for at least five years after the relevant filing deadline, because that's how far back HMRC can ask.
- If you're trading, decide early between the £1,000 allowance and deducting actual expenses — you can't use both, and for anyone spending more than £1,000 to earn the income, deducting real costs usually wins.
When you cross the line into self-assessment
Once your gross side income clears £1,000, the practical steps are straightforward but time-sensitive. You must register for self-assessment by 5 October following the end of the tax year in which you crossed the threshold — miss that and penalties start stacking up even before any tax is due. After registering, you file a return and pay any tax by the following 31 January.
The good news for most modest side-hustlers: registering doesn't mean a frightening bill. After the trading allowance or your actual expenses, and within your personal allowance if you've room left, the tax owed on a small side income is often a lot less than people fear. The penalty for not registering, by contrast, is real money for nothing. Register on time and the rest is admin; ignore it and the admin becomes a fine.
Being reported by a platform isn't a tax bill. The only thing that decides whether you owe is whether you were trading — and the records you keep are what prove which side of that line you're on.
This is general guidance, not advice on your specific circumstances — the right answer depends on what you sold, why, and how much. But the side-hustler who knows the £1,000 line, keeps a running record from day one, and registers on time if they cross it has nothing to fear from a platform report. The people who get hurt are the ones who either ignored a genuine obligation or worried themselves sick over a wardrobe clear-out that was never taxable in the first place.