Do you need to do a tax return for your online selling?

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Most people who sell online never need to fill in a tax return. You only need one if you're trading, meaning buying or making things to sell for a profit, and your sales go past the £1,000 trading allowance. If that's you, here's exactly what Self Assessment involves and the dates that matter.

First, do you even need to?

Two quick checks settle it for most people. If you were only selling your own used belongings, you don't need a return, however much it came to, because that isn't taxable. And if you were trading but your gross sales for the year stayed under £1,000, the trading allowance covers you, so again there's nothing to file.

You need to register only if you were trading and your gross trading sales topped £1,000 in the tax year. Not sure which camp you're in? The free checker tells you in a couple of minutes.

The three dates that matter

If you do need to do a return, the system runs on a few fixed dates. Tax years run from 6 April to 5 April, and everything keys off the year you went over.

Register by 5 October. You register for Self Assessment by the 5 October after the end of the tax year you went over £1,000. So if that was the 2025/26 year (ended 5 April 2026), you register by 5 October 2026. You only do this once, then you're in the system and get a tax reference.
File and pay by 31 January. You file your return online and pay any tax by the 31 January after that tax year. For 2025/26 that's 31 January 2027. (Paper returns are due by 31 October, but almost everyone files online.)
Possibly payments on account, 31 January and 31 July. If your tax bill is over £1,000, HMRC usually asks for two advance payments towards next year's bill, one on 31 January and one on 31 July. Worth knowing so the first January bill isn't a shock.

What you actually report

You report your trading income and your costs, and HMRC works out the tax on the profit. Profit is your sales minus your allowable costs (the stock, the platform fees, the postage), or minus the flat £1,000 allowance if that comes to more. You're taxed on that profit at your normal rate, once your £12,570 personal allowance is used up across all your income. On profit above £12,570 you'd also pay Class 4 National Insurance, at 6 percent up to £50,270 and 2 percent above.

The single best habit is to keep a simple running note through the year: what you sold, what it cost you, and the fees. Do that and the return is mostly a copy-and-paste job rather than a January scramble.

What's coming: Making Tax Digital

One change worth having on your radar, though it won't touch most sellers yet. From 6 April 2026, sole traders with qualifying income over £50,000 have to keep digital records and send HMRC quarterly updates, under Making Tax Digital for Income Tax. That threshold drops to over £30,000 from April 2027 and over £20,000 from April 2028. If your selling is nowhere near those figures, nothing changes for you for now, but it's the direction things are heading.

The "£3,000 change" in one line

You may have heard the reporting threshold is rising from £1,000 to £3,000. It is planned, but it has no start date yet, so £1,000 still applies today, and it changes how you report rather than how much you owe. There's more detail in our trading allowance guide.

Not sure if a return even applies to you?

Soldly asks a few plain questions and tells you straight: are you trading, are you over £1,000, do you need to register, and roughly what you'd owe. Two minutes, no sign-up, nothing saved.

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Common questions

Do I need to do a tax return for selling online?

Only if you're trading, meaning buying or making things to sell for a profit, and your gross trading sales for the tax year go over the £1,000 trading allowance. If you only sold your own used belongings, you don't need a return, however much it came to.

When do I need to register for Self Assessment?

By 5 October after the end of the tax year you went over £1,000. For example, if that happened in the 2025/26 tax year (which ended 5 April 2026), you register by 5 October 2026.

What's the deadline to file and pay?

You file your online return and pay any tax by 31 January after the tax year. For 2025/26 that's 31 January 2027. Paper returns are due earlier, by 31 October, but most people file online.

What do I report on the return?

Your trading income and costs, so HMRC can work out your profit. You're taxed on the profit (sales minus your costs, or minus the £1,000 allowance if that's bigger) at your normal rate, after your £12,570 personal allowance.