HMRC Has Data on 4 Million Online Sellers. And It’s Using It

Here’s my honest view, and I’ll back it up with the numbers in a minute. If you’ve been selling on eBay, Vinted, Etsy, Depop or Amazon without declaring the income, the game has changed. HMRC isn’t guessing anymore.

It has your name, your National Insurance number, your bank details, and a quarterly breakdown of every penny you took on the platform last year. That isn’t speculation. That’s what the law now requires the platforms to hand over, and they’ve handed it over. This crackdown is no longer a future threat, it’s already running. The only question left is whether you control how this ends, or whether it controls you.

The Numbers HMRC Has on Online Sellers in 2026

On 31 January 2026, every UK-facing digital platform submitted its second full year of seller data to HMRC. Figures obtained by accountancy firm BDO through a freedom of information request show that HMRC received reports on 3,988,892 online sellers for calendar year 2025. That’s nearly triple the 1,466,171 sellers reported the year before, a rise of around 172%.

The total gross earnings sitting in HMRC’s systems for 2025? Nearly £55 billion, up from £25.5 billion in 2024. Over 800 platforms are now reporting in.

3,988,892 Seller records held by HMRC for calendar year 2025

~£55bn Total gross earnings in HMRC’s systems for 2025

+172% Rise in seller reports from 2024 to 2025

800+ Digital platforms now submitting seller data to HMRC

Source: Figures obtained by BDO via Freedom of Information request, May 2026

What HMRC now holds on each reportable seller:

• Full name, address, date of birth
• National Insurance number
• Quarterly and annual gross sales figures
• Bank account details used to receive payments
• Fees and commissions withheld by the platform

This is the file the compliance team is now matching against your self-assessment return. Or, if you haven’t filed one, against the gap where your return should be.

I’ve been doing this work long enough to remember when the main enforcement tool against undeclared income from online selling was a polite request that you come forward voluntarily. That era’s over. The data’s in. Automated matching is being built. The first wave of nudge letters has already been sent, and a second wave is expected later in 2026 once HMRC finishes its matching system.

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Why I Don’t Think This Is Fearmongering

I’ll be the first to say a lot of online seller scare stories are overblown. Most of the people I meet who panic about selling on Vinted owe nothing. Selling your kids’ old clothes isn’t trading. Clearing out the loft isn’t trading. The casual disposal of personal possessions, even on a platform, isn’t what HMRC is hunting for.

But the picture changes the moment you start buying things in order to sell them, making things to sell, or selling services through a platform. That’s trade. It always has been. The only thing that’s changed is HMRC’s ability to see it.

If you’re confident your activity is genuinely casual and personal, you’ve got nothing to worry about. If you’ve been buying trainers wholesale and reselling them on eBay, running an Etsy shop with proper supply chains, or pulling in a few hundred a month flipping electronics on an online marketplace, the data HMRC now holds will tell that story for you.

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Am I Trading or Just Selling Old Stuff?

This is the question I get asked more than any other. It deserves a straight answer.

HMRC uses what it calls the badges of trade, set out in its Business Income Manual (BIM20205). There are nine, but in practice four matter for online selling:

• Profit motive. Did you buy or make this thing in order to sell it at a profit?
• Number and frequency of transactions. Are you doing this regularly and systematically, or did you sell three things last year?
• Nature of the asset. Was it something you owned and used personally, or stock acquired with resale in mind?
• Interval between purchase and sale. Did you hold it for years, or buy it Tuesday and list it Wednesday?

No single badge decides it. HMRC weighs the whole picture. But the common pattern looks like this. Selling your old wardrobe on Vinted? Not trading. Buying job lots of clothing on Facebook Marketplace and listing them on Vinted at a markup? That’s trading from item one. Selling handmade candles, soap, prints or jewellery on Etsy? Almost always trading, because you produced the goods specifically to sell.

If HMRC decides you’re trading, you’re effectively a self-employed sole trader for tax purposes, and Self Assessment applies from day one. If you genuinely don’t know which side of the line you’re on, that’s exactly the kind of thing to bring to an accountant before HMRC’s letter forces the conversation. If you’re already compliant and just want to run your side hustle properly, see our guide to how to manage the finances of your side hustle.

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What the £1,000 Trading Allowance Actually Covers

Here’s where I see the most expensive misunderstandings.

The £1,000 trading allowance is a real thing, and it’s useful. If your gross trading income across the entire tax year is £1,000 or less, you owe no tax and you don’t have to tell HMRC anything. No registration, no return, no problem.

But three rules trip people up constantly.

Rule one: it’s gross, not profit. The £1,000 ceiling is what you took in before fees, postage, packaging or the cost of the stock. If your eBay receipts are £1,400 and your costs are £900, you cleared £500. You still have to register for Self Assessment as a sole trader, because gross income exceeded £1,000.

Rule two: it aggregates across every platform you sell on. Picture Tom, a graphic designer who sold £1,200 on Depop and £950 on Etsy in 2024-25. Each platform individually sat below £1,000, so he assumed he was safe. He wasn’t. The trading allowance rules apply to total trading income, not per-platform. Combined gross of £2,150 puts him well over the threshold. He should have registered for Self Assessment by 5 October 2025. Once you add the failure to notify penalty and interest, a tax bill that started at about £230 ended up over £330. Small money, but entirely avoidable.

Rule three: it doesn’t apply if your income is paid by your employer, a company you control, or a partnership you’re in. Side jobs from your day job employer are taxed from the first pound.

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The “I’m Under the Platform Threshold” Misconception

The other line I hear is, “I only made about a thousand on eBay, I’m not at the 30 transactions or €2,000 mark, so the platform won’t report me.” That misses the point of the rules.

The 30 sales and €2,000 (approximately £1,700) threshold determines whether the platform has to send your data to HMRC. It doesn’t determine whether you owe tax. Those are two entirely separate questions.

Your tax obligation is set by UK domestic law and turns on whether you’re trading and how much trading income you’ve earned. Whether your platform reported you is a separate matter that affects how easily HMRC can match data to your records. If you’re trading and you’re over £1,000 gross, you owe tax regardless of whether the platform passed your details along. And the platform reporting rules will catch most genuine traders anyway.

I’d also add this. If you’re flying just under the platform threshold deliberately, splitting sales across multiple accounts, or using a friend’s profile to keep the numbers down, you’re not being clever. You’re documenting deliberate behaviour. The penalty bands for deliberate non-disclosure of undeclared income start at 20% and go to 100% of the tax owed. The lookback runs to 20 years. There’s no version of that maths that works in your favour.

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What HMRC Actually Does With the Data on Online Sellers

Right now, the automated matching system is being built. BDO’s May 2026 commentary confirms HMRC is in the final stages of building a system that will cross-reference platform reports against self-assessment returns and flag mismatches. Anyone trading online effectively functions as a self-employed sole trader for tax purposes, which means their earnings should already appear on a Self Assessment return. That covers the ecommerce side of things whether you’re shifting stock on Amazon, running an Etsy shop, or moonlighting on Depop.

The first practical output you’ll see, if it lands in your name, is what HMRC calls a one-to-many letter. We sometimes call them nudge letters. The first wave went out in late February 2025, aimed at marketplace sellers HMRC’s existing data suggested had undeclared income for years up to and including 5 April 2023.

The letter is not a formal enquiry. It doesn’t accuse you of anything. It does three things:

• Tells you HMRC holds information suggesting you may have unreported income
• Gives you 30 days to declare or contact HMRC
• Warns that failing to respond may trigger a formal compliance check with higher penalties attached

In practice, once a nudge letter lands on your doormat, HMRC will almost always treat any subsequent disclosure as prompted. Some advisers argue it shouldn’t be. HMRC’s own Compliance Handbook at CH82421 says a national campaign isn’t automatically enough to convert disclosures to prompted. But you don’t want to be the test case on that point. That single classification shifts your minimum careless penalty from 0% to 15%. We’ll come back to it, because it’s the most expensive sentence in this article.

If a new wave of letters arrives later in 2026, expect them to be wider, more confident, and to cite specific platform totals. HMRC will know your gross figures down to the quarter.

1 Jan 2024		Platform reporting rules take effect SI 2023/817 comes into force. Platforms begin collecting seller data.
31 Jan 2025		First platform data submitted to HMRC Covers calendar year 2024. HMRC receives 1,466,171 seller reports.
27 Feb 2025		First wave of HMRC nudge letters issued Targets sellers with undeclared income through tax year ending 5 April 2023. Recipients given 30 days to respond.
31 Jan 2026		Second platform data submitted to HMRC Covers calendar year 2025. HMRC now holds data on 3,988,892 sellers and nearly £55 billion in gross earnings.
Mid-2026		Automated matching system expected to go live HMRC cross-references platform data against Self Assessment returns. Second wave of letters expected, citing specific platform totals by quarter.
Now		The window to come forward on your own terms Unprompted disclosures can still attract 0% penalty on careless underpayments. Once a letter arrives, the minimum penalty floor rises to 15%.

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What If HMRC Sends Me a Letter?

First: don’t panic, but don’t put it in a drawer either. The 30-day reply window matters.

Second: read it carefully. The letter will tell you what tax years HMRC’s interested in and what HMRC believes about your activity. It will direct you to the Digital Disclosure Service or to “Tell HMRC about underpaid tax from previous years.”

Third: work out, quickly and honestly, whether you actually owe anything. There are three possible positions.

Position one: You were genuinely selling personal possessions. No trading activity. No tax due. You still need to respond, but the reply’s straightforward: confirm the activity was personal disposal, set out the items in summary, and the matter usually closes. Take Sarah, a nurse in Norwich, who gets a nudge letter after selling 45 household items for £2,400 in 2023. None of the items were bought to resell, all were personal property, none individually worth over the £6,000 chattel exemption. Zero tax due. The right reply, drafted properly, closes the file. Worry is the only cost.

Position two: You were trading, you knew it, and you didn’t declare. You need to make a full voluntary disclosure now. The longer you wait, the higher the penalty band and the more interest accrues.

Position three: You’re not sure. This is most people. The right move is to get an hour with someone who can look at your records and tell you which position you’re in before you reply. Thirty days is enough time to do that.

The worst response to a nudge letter is no response. HMRC reads silence as cause to open a formal check, and the penalty position only gets worse from there.

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Unprompted vs Prompted Disclosure: What Online Sellers Need to Know About HMRC Penalties

Here’s the part of this story that costs people the most money, and that they almost never think about until it’s too late.

HMRC’s penalty regime distinguishes between unprompted disclosures (you came forward before HMRC contacted you about it) and prompted disclosures (HMRC contacted you first, or you came forward only after their letter). The difference looks like this:

For most casual or side hustle non-disclosure, the relevant row is the top one. A seller who comes forward voluntarily and cooperates fully can land at 0% penalty on the underpaid tax. The same seller who waits until HMRC writes is looking at at least 15%, often more.

If Jake came forward first £1,210 £1,090 tax + £120 interest Penalty: £0 (careless, unprompted, full cooperation)

vs

After HMRC’s nudge letter £1,374 £1,090 tax + £120 interest Penalty: £164 (careless, prompted, 15% minimum)

Jake’s case: eBay/Vinted trainer reseller, 5 years undeclared, £5,450 total profit. Penalty position turns entirely on who made contact first.

The £164 difference is the price of three months of putting it off. And that’s a small-money example. Scale it up to a higher-rate Etsy seller with £15,000 of undeclared profits across three years, and the prompted vs unprompted gap is the difference between a £400 penalty and a £900-plus penalty, before interest compounds it further.

The timing isn’t a technicality. It’s the single biggest lever you have over the outcome.

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What Online Sellers Should Do in the Next 30 Days

If any of this applies to you, here’s the practical sequence. Not a vague checklist. The actual steps in the actual order.

1. Pull your platform data. Every major platform now lets you download your seller statement for past calendar years. eBay, Etsy, Vinted, Depop, Amazon, Airbnb, all of it. Get the figures for every year you’ve been active, not just the most recent. You can’t disclose what you can’t see.

2. Reconcile calendar year to tax year. The platforms report on calendar year (1 January to 31 December). UK Self Assessment runs on tax year (6 April to 5 April). You’ll need to split each platform year into the two tax years it covers. So income earned on eBay between 1 January 2025 and 5 April 2025 falls in the 2024-25 tax year, while income from 6 April 2025 to 31 December 2025 falls in the 2025-26 tax year. Spreadsheet time. If you’ll be filing Self Assessment for the first time, be aware that Making Tax Digital for sole traders takes effect from April 2026 for those with gross qualifying income over £50,000 (the threshold falls to £30,000 from April 2027, then £20,000 from April 2028) and may affect how you submit returns going forward.

3. Identify your real cost base. Stock purchases, platform fees, postage, packaging, payment processor charges. Bank statements and PayPal records are your friend here. If you can evidence costs, you reduce taxable profit. If you can’t evidence them, you may be better off claiming the £1,000 trading allowance instead.

4. Work out the tax for each year. Apply your marginal rate. Most self-employed side hustle sellers are basic-rate taxpayers paying 20% on profits over their personal allowance. Higher-rate sellers pay 40%. Class 4 National Insurance at 6% may apply on profits between £12,570 and £50,270 for 2025-26, with 2% above that.

5. Decide your route. A single late tax return covers a missed current year. The Digital Disclosure Service covers multiple back years and is the right route for anyone with two or more years of undeclared income. The DDS gives you 90 days from notification to submit the full disclosure, which is enough time to do the job properly.

6. Notify before HMRC notifies you. This is the lever. Once you’ve registered intent to disclose through the DDS, you’ve locked in the unprompted status, which protects the lowest penalty band even if the actual disclosure takes the full 90 days.

7. Get advice if the bill could go above a few hundred pounds. A one-hour consultation pays for itself many times over on multi-year disclosures, particularly where the calendar-year-to-tax-year reconciliation gets complex or where the trading-versus-personal-possession line is genuinely arguable.

The cost of doing this properly is small. The cost of doing it badly, or not doing it at all, scales with every month that passes.

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My Bottom Line

I’ll say it plainly because that’s how I’d say it across the desk.

HMRC isn’t going to forget the 3,988,892 seller records sitting in its system. The matching’s being automated. The next wave of letters is coming. And the moment one lands on your doormat, your penalty floor effectively jumps from zero to fifteen per cent, and your control over the conversation effectively ends.

If you owe nothing, this article isn’t about you. Sell your old stuff, enjoy the extra fifty quid, sleep well.

If you might owe something, the work to find out is one evening with your platform statements and a calculator. The work to fix it is a few hours and the right route through HMRC’s systems. The cost of doing it now versus later is measured in real money.

We work with a lot of ecommerce sellers through our eCommerce accounting service, from first-time Self Assessment filers to established Etsy and Amazon businesses juggling quarterly MTD submissions. If this affects your business or your side hustle and you want a clear-eyed view of where you actually stand, get in touch. This is exactly the kind of thing we work through with clients every week, and the earlier in the conversation we start, the more options remain on the table.

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Frequently Asked Questions About HMRC and Online Sellers in 2026

What Are the New HMRC Rules for Online Sellers in 2026?

The rules themselves haven’t changed in 2026, but enforcement has. Since January 2024, digital platforms must send HMRC the name, NI number, bank details and gross sales of any seller hitting 30 sales or roughly £1,700 a year. For 2025, nearly 4 million online sellers were reported, and HMRC’s matching system is expected to go live this year. See “The Numbers HMRC Has on Online Sellers in 2026” above for the full picture.

What Is the New UK Digital Sales Reporting Threshold for 2026?

The platform reporting threshold is 30 transactions or €2,000 (about £1,700) per seller per calendar year. Separately, the £1,000 trading allowance still governs whether you personally owe tax and need to register for Self Assessment. The two thresholds get confused constantly, see “The ‘I’m Under the Platform Threshold’ Misconception” above for why they’re not the same thing.

Are New HMRC Rules for 2026 Different to Previous Years?

The underlying tax rules for sole trader online sellers are the same. What’s different in 2026 is the data: HMRC now has a second full year of platform reports covering 3.99 million sellers, and the automated cross-matching against Self Assessment returns is rolling out this year. A second wave of nudge letters is expected later in 2026, and the government has separately announced plans to take 300,000 side hustlers out of Self Assessment by lifting the reporting threshold, though that change hasn’t taken effect yet.

Is HMRC Going After eBay Sellers Specifically?

No, this crackdown covers every reportable digital platform: eBay, Vinted, Etsy, Depop, Amazon, Airbnb, and around 800 others. HMRC isn’t targeting one marketplace, it’s matching all platform data against tax records. If you’re genuinely selling personal items you’ve nothing to worry about. See “Why I Don’t Think This Is Fearmongering” above for where the line sits.