Do you need to register for Self Assessment by 5 October?

Quick answer

• You need to register by 5 October 2026 if, between 6 April 2025 and 5 April 2026, you sold more than £1,000 worth of things you bought to sell on, or made to sell. That's trading.
• You don't need to register if you were selling your own belongings: clothes you wore, the exercise bike, the loft clear-out. That isn't trading, whatever Vinted reported.
• Registering isn't paying. It gets you a reference number so you can file a return by 31 January 2027. Most people who register find they owe little or nothing.
• Missed 5 October? Register now anyway. Penalties are worked out on tax unpaid after 31 January, so file and pay on time and there's usually nothing extra to pay.
• The "£3,000 threshold" has no start date. Today the line is £1,000.

Why 5 October

HMRC's rule is simple: if you've got a new source of income that isn't taxed at source, you tell them by 5 October after the end of the tax year it started in. The 2025/26 tax year ended on 5 April 2026, so the date is 5 October 2026. HMRC said it again in July, in its own words: "new entrants to Self Assessment should register for the 2025 to 2026 tax year by 5 October 2026."

Registering isn't paying. It's HMRC giving you a reference number so you can file a return by 31 January 2027, and pay whatever's due by the same day. Registering by 5 October and then finding out you owe nothing is completely normal. It happens to most people who do it.

Are you trading, or just selling?

HMRC doesn't count items or care which app you use. It asks whether what you're doing looks like a business. The tells:

• You bought things in order to sell them on. Car boot finds, charity shop flips, wholesale lots, bundles you split.
• You made things to sell. Prints, candles, upcycled furniture, crochet.
• You sell regularly, price for profit, or top up stock when it runs low.

If none of that is you and you're selling things you owned and used, you're not trading. Volume doesn't change that. Fifty items from your own wardrobe in a year is still your own wardrobe.

One wrinkle for the not-trading crowd: if a single possession sold for more than £6,000 (a watch, a painting, a set of something), that's a possible capital gains question, not a trading one. Rare, but worth knowing.

The £1,000 line

Everyone gets a £1,000 trading allowance. If your total trading sales in the tax year were £1,000 or less, you don't need to tell HMRC or register, full stop. Above that, you register, and when you file you choose one of two ways to work out your profit: take off the £1,000 allowance, or take off your actual costs (what you paid for stock, postage, packaging, fees). One or the other, not both. For most small sellers whose costs are more than £1,000, the actual costs win.

"I heard I don't need to do anything under £3,000"

You heard wrong, and you're in good company. The government has announced a plan to raise the point at which you must file a full return from £1,000 to £3,000 of trading income. It has no start date, and a new online reporting tool is promised "by 2029". Until then, £1,000 is the line.

"Vinted reported me, so I must owe something"

No. Vinted, eBay and Depop now send HMRC a record of any seller who makes 30 or more sales in a calendar year, or takes about £1,700 (€2,000) or more. That is a reporting rule, and it catches thousands of people clearing out wardrobes. Being on the list doesn't mean you owe tax, and it doesn't mean you need to register. Whether you're trading, and whether you're over £1,000, is what decides it. The platform will send you a copy of what it reported, by 31 January. Keep it; it's useful when you file.

How to register (about fifteen minutes, then a wait)

• Go to GOV.UK and search "register for Self Assessment". Choose the self-employed (sole trader) route; that's what a reseller is.
• You'll need your National Insurance number, your address, the date you started selling to make a profit, and a description of what you do ("online reselling of second-hand goods" is fine).
• HMRC posts you a Unique Taxpayer Reference (UTR). Allow ten working days, longer near deadlines. Then you activate your online account with the code they send.
• You then have until 31 January 2027 to file the return and pay. You can do it in November and forget about it.

If you've already missed 5 October

Register anyway, today. The penalty for telling HMRC late is worked out on tax that's still unpaid after 31 January. Register late but file and pay by 31 January and, in the usual case, there's nothing to pay in penalties at all. Don't let a missed date turn into a missed return; that's where the real fines are.

What you'll actually owe (roughly)

Your profit is your sales minus your costs (or minus the £1,000 allowance). If your total income for the year, job included, stays under £12,570, there's no income tax. Above that, 20% on the profit until you reach £50,270. If your trading profit on its own is over £12,570 you'll also pay Class 4 National Insurance at 6% on the part above it. Below a profit of £7,105 you don't have to pay Class 2 National Insurance either, though you can choose to for £3.65 a week to protect your state pension record.