Your First Self Assessment / Lesson 5 of 7
Selling online: when it becomes trading
Priya got a letter about her Vinted sales. She had done nothing wrong.
The short answer
- ✓ Selling your own used possessions is not trading, whatever the total
- ✓ Platform reporting shows sales volume, not whether you were trading
- ✓ Buying in order to sell is the clearest sign of trading
- ✓ Do not register for Self Assessment out of panic: it creates a lasting obligation
What happened to Priya
Priya cleared out her wardrobe and sold around £2,800 of her own clothes over a year. Months later a letter arrived referring to information from an online platform about her sales.
She owed nothing. Selling your own used possessions is not trading, whatever the total. But the letter was alarming, and she nearly registered for Self Assessment out of panic, which would have created an obligation she did not have.
Why the letters started
Digital platforms now report seller information to HMRC. That reporting says what you sold. It says nothing about whether you were trading, because the platform has no idea whether you bought the item to resell or wore it for five years.
So HMRC is receiving volume data without context, and some of the follow-up lands on people who owe nothing.
The distinction that decides it
| What you did | Trading? |
|---|---|
| Sold clothes you had worn | No |
| Sold furniture when moving house | No |
| Bought items at car boots to resell at a profit | Yes |
| Made things to sell | Yes |
| Bought in bulk and split into single units | Yes |
| Sold a gift you did not want | No |
The question is what you did, not how much came in. Intention and pattern decide it: buying in order to sell is the clearest indicator of trading.
If you are trading
The trading allowance covers the first £1,000 of income. Above that you register and file, and the earlier courses in this Academy cover exactly what that involves.
Sales income £3,400 <- over the allowance
Cost of stock £1,900
Fees and postage £420
--------
Taxable profit £1,080
Taxed at your marginal rate, which for an
employee usually means 20% or 40%, plus Class 4 NI.The bit HMRC does not spell out
Receiving a letter is not an accusation and it does not require you to register. If you were selling your own possessions, reply and explain that. Registering for Self Assessment when you do not need to is worse than doing nothing: it creates an annual filing obligation that persists until you cancel it, with penalties for each year you then fail to file.
Answer the letter. Do not panic-register.
Common mistakes
- Panic-registering after a letter. It creates an obligation you may not have.
- Assuming a high total means trading. The test is what you did.
- Ignoring the letter entirely. Reply and explain.
- Testing the allowance on profit. It is on income before costs.
Try it on your own numbers
This is the same calculator as the full tool page, using 2026/27 rates.
Your side hustle
Tax on a second income (freelancing, selling, gig work) stacked on top of your main job. Updates as you type.
Includes the £1,000 trading allowance. The "best of both" option uses whichever of the allowance or your real expenses saves you more - you cannot claim both.
Tax on your side hustle
on of side income - you keep
- Deduction used
- Taxable side profit
- Income Tax on it
- Class 4 NI on it
- You keep
kept of side income
tax on next £100
Register for Self Assessment
Your side income is over £1,000, so you must register with HMRC and file a tax return.
Estimate only. Assumes Class 4 NI; small profits may also owe voluntary Class 2.
Tax as your side income grows
How your take-home and tax change as the side hustle scales, on a salary.
Compare saved scenarios
| Scenario | Side income | Tax + NI | You keep | |
|---|---|---|---|---|
Key takeaways
- ✓ Selling your own used possessions is not trading, whatever the total
- ✓ Platform reporting shows sales volume, not whether you were trading
- ✓ Buying in order to sell is the clearest sign of trading
- ✓ Do not register for Self Assessment out of panic: it creates a lasting obligation
Check you have got it
3 quick questions. No score is kept, and you can change your mind.
1. You sold £2,800 of your own worn clothes. Do you owe tax?
2. What does platform reporting to HMRC actually show?
3. You receive a letter but were only selling your own things. What is the right response?
Sources
Finished this lesson?
Mark it done and we will remember where you got to.
You are 5 lessons in. Want to keep your progress?
Right now your place is saved in this browser only. A free account keeps it across devices, unlocks the end-of-course exam and certificate, and gives you a personal action plan at the end. No card, no upsell.
