If you’ve recently started selling on Whatnot, eBay, Vinted or another marketplace, there’s a point where something that started as a bit of extra money can become a business.
And that brings us to everybody’s favourite subject: tax.
For new resellers, HMRC can sound far more complicated than it needs to be. Terms like trading allowance, Self Assessment and taxable income aren’t exactly beginner-friendly.
So let’s strip the jargon away and explain the bit every new reseller should understand.
First: selling things doesn't automatically make you a business
There’s an important difference between selling your own unwanted belongings and buying things with the intention of reselling them for profit.
If you're having a clear-out and selling old clothes, toys, trainers or other possessions you no longer want, you generally aren't suddenly running a business just because you've sold them online.
Reselling is different.
If you're buying stock from a wholesaler, visiting car boots looking for things to flip, buying clearance stock or deliberately sourcing products because you think you can sell them for more, you're potentially trading.
That's when you need to start paying attention to HMRC.
The £1,000 rule that confuses everyone
There is currently a £1,000 trading allowance.
The really important thing to understand is that this refers to trading income, not profit.
Let's put that into reseller language.
Imagine you spend £700 buying stock.
You eventually sell that stock for £1,200.
You haven't made £1,200 profit. Obviously.
But your trading income is still £1,200.
You've therefore gone over the £1,000 trading allowance and may need to tell HMRC.
That's one of the biggest misunderstandings new resellers can make.
Does earning £1,001 mean I suddenly owe loads of tax?
No.
Going over £1,000 in trading income does not automatically mean you owe tax on everything you've sold.
Whether you actually have tax to pay depends on your individual circumstances, including your profits, expenses, other income and the tax allowances available to you.
Think of these as two separate questions:
Do I need to tell HMRC?
and
Do I actually owe HMRC money?
They're not necessarily the same thing.
Sales aren't the same thing as profit
This is another concept every new reseller should learn early.
Suppose your Whatnot account shows you've sold £10,000 worth of products.
That doesn't mean you've made £10,000.
You might have spent thousands buying those products in the first place.
Then there could be platform fees, packaging, postage and other costs associated with running your business.
What's left after your allowable business expenses is much closer to understanding the actual profit your business has generated.
That's why good record keeping matters.
“But I only sell on Whatnot. How would HMRC know?”
This isn't a good strategy for running a business.
Online marketplaces are increasingly required to provide information about sellers to tax authorities under international reporting rules.
That doesn't mean HMRC is going after everyone who sells an old jumper online.
It means sellers shouldn't assume that money earned through an online marketplace is somehow invisible.
If you're building a genuine reselling business, start treating it like one.
Get into this habit from your first sale
You don't need an enormous accounting system when you've just started.
But you do need records.
Keep track of:
what you bought
how much you paid
what you sold it for
platform fees
postage
packaging
other costs associated with your business
And keep your receipts and invoices.
It might feel unnecessary when you've only sold £200 worth of stock.
It won't feel unnecessary when you've made hundreds or thousands of transactions and you're trying to remember what you paid for something eight months ago.
What if I also have a normal job?
That's extremely common.
You can have a PAYE job and also run a reselling business on the side.
Your employer normally handles tax on your wages through PAYE.
Your reselling income is different because you're generally responsible for dealing with any tax obligations relating to that activity yourself.
That's why it's called a side hustle—but HMRC doesn't stop caring about it because it's happening in the evening after work.
Important dates for new sellers
According to the information provided for the 2025/26 tax year, someone who is new to Self Assessment and needs to register must do so by:
5 October 2026
The online tax return and any tax due would then need to be dealt with by:
31 January 2027
Don't leave learning about this until January.
What about the new £3,000 limit I've heard about?
This is another area where it's very easy to get confused.
The Government has announced plans to increase the Self Assessment reporting threshold for trading income from £1,000 to £3,000.
But the change has not yet come into force, according to the source material we're explaining here.
More importantly, the proposal does not mean people will simply be able to earn £3,000 tax-free.
The £1,000 trading allowance is a separate issue.
The proposed change is intended to reduce the number of people who need to complete a full Self Assessment return, with a simpler system planned for some people who still owe tax.
Until those changes actually take effect, don't assume you can simply earn £3,000 without doing anything.
A simple example
Meet Sarah.
Sarah works during the week but has recently started selling beauty products online.
She buys £600 of stock.
Over the tax year she sells it for £1,400.
A common beginner mistake would be:
“I only made £800, so I'm under the £1,000 limit.”
But that's mixing up sales and profit.
Her trading income was £1,400.
Her stock cost is relevant when working out her business profit and potential tax position, but it doesn't turn her £1,400 of trading income into £800 for the purpose of deciding whether she's crossed the £1,000 trading-income threshold described above.
That's why understanding the difference matters.
Don't be frightened of HMRC — just don't ignore it
If you're new to reselling, seeing words like HMRC and Self Assessment can make running a small business suddenly sound terrifying.
It doesn't need to be.
You don't need to become an accountant.
You need to understand the basics, keep decent records and ask for proper help when you're unsure.
And perhaps the most important lesson is this:
Don't wait until your reselling business becomes successful before you start treating it like a business.
Build good habits while it's small.
Because if your £500 side hustle eventually becomes a £50,000 business, you'll be very glad you did.
The Reseller Vault UK takeaway
Selling your old belongings ≠ automatically running a business.
Buying stock specifically to resell for profit = you may be trading.
£1,000 trading allowance = based on trading income, not simply your profit.
Going over £1,000 = doesn't automatically mean you owe tax.
Keeping records from day one = very good idea.
And if you're unsure about your own circumstances, check directly with HMRC or speak to a qualified tax professional rather than relying on advice from Facebook, TikTok or another seller.
This article is intended as general educational information for UK resellers and isn't individual tax or financial advice.