When HMRC Writes About Your Online Sales: A Calm Response Plan for 2026

For many people who sell online, the first contact with the tax system arrives as an unremarkable brown envelope rather than a tax return. HMRC has been receiving bulk seller data from UK digital platforms since early 2025, and by 2026 the matching exercise is routine. The letter that follows is rarely an accusation. It is an invitation to check your position — and how you respond in the first few weeks matters far more than most recipients realise.

Why the letter has arrived now

Platforms operating in the UK are required to collect and report information about sellers under rules implementing the OECD's Model Reporting Rules for Digital Platforms. The report covers a calendar year and is passed to HMRC by the end of the following January. It typically includes your name, address, taxpayer identification number, the gross value of sales, the number of transactions, and the fees and commissions deducted by the platform.

Two features of that data catch people out. First, it is reported gross — before platform fees, postage and the cost of whatever was sold. Second, it says nothing about whether the activity was a trade. HMRC then matches the data against self assessment records. Where a seller has no return on file, or where reported figures exceed the turnover declared, an information letter may be issued.

The letter is not an assessment

These letters — sometimes described as nudge letters — generally ask you to review the income reported by the platform, confirm whether it has been declared, and reply within a set period, often 30 days. Some versions ask for a completed certificate confirming your position.

It is important to be clear about status. The letter does not, by itself, create a tax liability, and it is not a formal enquiry. It is a prompt. Ignoring it, however, invites escalation: a failure to respond can lead to a compliance check being opened, at which point the tone and the burden of proof change considerably.

Deciding whether you were trading

This is the substantive question, and it is a question of fact rather than of how much money changed hands. HMRC looks at a series of indicators, often called the badges of trade:

• Motive. Did you buy with a view to selling at a profit, or were you recovering some of the cost of things you already owned?
• Repetition. A single wardrobe clear-out looks very different from weekly listings over twelve months.
• Organisation. Stock storage, packaging materials, spreadsheet records, a dedicated selling account and a deliberate pricing strategy all point towards trading.
• Subject matter. Selling fifty identical new items is not the same as selling fifty second-hand ones.
• Alteration. Refurbishing, repairing, repurposing or bundling goods before sale suggests a trading operation.
• Holding period. Items bought and resold quickly look more like stock than possessions.

Selling your own used clothes, books or furniture is not, in itself, taxable trading. Personal possessions sold at a gain are generally exempt from capital gains tax where each item is sold for £6,000 or less, and wasting assets such as cars are outside the charge altogether.

Two short illustrations

Priya spends a weekend clearing her wardrobe onto Vinted. Across the year her gross sales reach £2,400, all from clothes and shoes she bought for herself in previous years and sold at a fraction of their cost. She is realising personal assets, not trading. No income tax is due and no return is required on this account — but she should still reply to HMRC explaining the position and keep the platform statements as evidence.

Tom buys mixed bundles at car boot sales for around £600 and resells individual items on eBay, listing most weeks. Gross sales are £3,100. The repetition, the purchase with resale in mind and the sorting and listing process make this a trade.

Using the £1,000 trading allowance correctly

Every individual has a £1,000 trading allowance and a separate £1,000 property allowance. The trading allowance is widely misunderstood, so three points are worth setting out plainly.

First, if your trading income is £1,000 or less, that income is not taxable and you do not need to tell HMRC about it or file a return on its account.

Second, once income exceeds £1,000, the allowance does not taper. You may deduct a flat £1,000 instead of your actual expenses — that is the whole of the relief.

Third, it is an alternative to expenses, not an addition. If you claim the allowance you cannot also deduct platform fees, postage, packaging or capital allowances. For most sellers with meaningful costs, claiming actual expenses produces the lower taxable figure. The allowance is most useful where record-keeping has been patchy or where expenses are genuinely minimal.

The allowance is also not available against income from an employer or a connected party.

Returning to Tom: his gross income is £3,100. Claiming the allowance gives taxable profit of £2,100. If his actual costs — stock, postage, packaging, a proportion of home broadband — came to £1,300, deducting those instead would give £1,800, which is better still.

A step-by-step response

1. Download the platform statement. eBay, Etsy and Vinted all provide annual summaries, usually released in January or February. Save the PDF rather than relying on the dashboard.
2. Reconcile it to your bank account. Identify fees, refunds, postage and any sales that were cancelled.
3. Classify your activity. Personal disposals, a hobby with no profit motive, an established trade, or a trade already declared elsewhere.
4. Calculate the taxable figure. Gross sales, less allowable costs or the £1,000 allowance, whichever is lower.
5. Correct your position. If you have already filed a return, you can normally amend it within twelve months of the filing deadline. If you have never registered, the deadline for notifying chargeability is 5 October following the end of the tax year. Where several years are involved, HMRC's Digital Disclosure Service allows a single voluntary disclosure with reduced penalties.
6. Reply in writing and keep a copy. A short, factual letter setting out your conclusion, the figures and the basis for it closes most of these cases quickly.

Penalties and why speed helps

Failure to notify HMRC of taxable income can attract a penalty of up to 100% of the tax due, scaled by behaviour and by whether disclosure was unprompted or prompted. A prompt, accurate and unprompted response sits at the favourable end of that framework. Delay, or a reply that contradicts the platform data without explanation, does not.

Records worth keeping

Retain platform statements, bank records, purchase receipts and a simple log of costs for at least five years after the 31 January filing deadline for the relevant year. For anyone selling regularly, a separate bank account for the activity removes most of the reconciliation work at a stroke — and makes a future letter very much easier to answer.