If a selling app has asked for your National Insurance number, date of birth or home address, you're not alone. Under UK rules that started on 1 January 2024, digital platforms may need to collect these details from sellers, check them, and report some sellers to HMRC. This guide explains what GOV.UK says the platforms must collect, why the request can appear near the end of the year, and what you get back. It sticks to GOV.UK's own guidance.
The short answer
GOV.UK's guidance for sellers, selling goods or services on a digital platform, says the platform operator "may need to":
- "collect and check specific details about you"
- "report details to HMRC"
The National Insurance number is the "tax identification number" the rules use for sellers who live in the UK. GOV.UK also says that a platform reporting your details "does not automatically mean you owe tax".
What platforms ask individual sellers for
GOV.UK says that if you're an individual seller, the platform will ask for your:
- full name
- address where you normally live
- date of birth
- "tax identification number (National Insurance number if you live in the UK)"
It also needs to know which country issued your tax identification number. Platforms "may ask you for other information if they need it to register you on the platform, like a phone number or email address", and "may ask you for other details to help them to confirm your identity".
Not selling as an individual? GOV.UK says a company gives its legal business name, main business address and company registration number. A UK partnership gives its partnership Unique Taxpayer Reference (UTR).
Why the request can come late in the year
The rules run on calendar years. GOV.UK's guidance for platforms says they "need to collect seller information by 31 December of the reportable period, which runs from 1 January to 31 December". Then, by the following January, they report to HMRC. GOV.UK's example: information about 1 January to 31 December 2024 "will be reported to HMRC by 31 January 2025".
So for 2026, platforms are collecting details up to 31 December 2026, and reporting by 31 January 2027.
Platforms also have to check what you give them. GOV.UK says they only need more information to verify a National Insurance number if they're unsure it's reliable ("for example, if a National Insurance number is missing a character"), or if HMRC has told them it's wrong. That's one reason you might be asked a second time.
If you don't provide it
GOV.UK's guidance to platforms says: "If a seller refuses to provide information, you may decide to take action to get the information. For example, you may temporarily limit their access to your platform until they have provided the correct information."
How each platform handles this is up to that platform. Check its own help pages.
Being asked is not the same as being reported
Platforms collect details from sellers, but not every seller is reported. GOV.UK tells platforms they don't need to report sellers of goods who get "a total of 2,000 euros or less (approximately £1,700) for fewer than 30 sales of goods in a year". That exception doesn't cover services or rentals. Our guide Do Vinted and eBay report you to HMRC? goes through the exception in detail.
What you get back if you're reported
GOV.UK says: "Platform operators have to give you a copy of the information they have reported to HMRC." That copy:
- shows "the total amount that you have earned on the platform for the calendar year, less any fees, commission or taxes deducted by the platform"
- breaks the amounts into quarters of the calendar year
GOV.UK adds that the reports "do not replace your normal business records or tax calculations". It also says: "If you do need to tell HMRC about your income, you'll need to work out your income for the tax year (6 April to 5 April)."
Worked example (made-up figures)
Jess sells on one app. Every figure here is invented. After 2026 ends, the app gives her a copy of what it reported for calendar year 2026:
| 2026 quarter | Months | Amount after fees |
|---|---|---|
| Q1 | January to March | £300 |
| Q2 | April to June | £400 |
| Q3 | July to September | £200 |
| Q4 | October to December | £100 |
| Total | £1,000 |
Now compare that with the tax years:
- 2025–26 ended on 5 April 2026. It includes all of Q1 and the first five days of Q2.
- 2026–27 started on 6 April 2026. It includes the rest of Q2, plus Q3 and Q4.
Q2 straddles the two tax years, so the quarterly figures can't be split at 5 April. To get a figure for each tax year, Jess needs her own sales history, with a date on every sale. The platform's figure is also after fees, so it may differ from a total of her sale prices. Which figures matter for her, if any, is for her to check against GOV.UK's guidance.
Personal items or trading?
Being asked for your National Insurance number says nothing about whether you owe tax. GOV.UK says that to pay tax on the goods or services you sell online, you must be either "trading" or "making a capital gain". It also says:
"You're unlikely to pay tax if you sell personal items from your home, like contents of a loft or garage."
"If you buy or make goods to sell at a profit, you're likely to be trading and will have to pay tax on your profits."
Which describes your selling is for you to work out. GOV.UK's check if you need to tell HMRC about your income from online platforms is the place to start, or ask HMRC or an accountant.
FAQ
Does giving my National Insurance number mean I have to do a tax return? Not by itself. GOV.UK says a platform reporting your details "does not automatically mean you owe tax". Whether you need to tell HMRC depends on the rules in the guidance above.
I sell on three apps. Will each one ask? The duty sits with each platform. GOV.UK tells operators to collect information "about sellers on your platform", so each app you sell on may ask, and each one reports separately.
I live outside the UK. What happens? GOV.UK says: "HMRC will share your information with your country's tax authority if you live in another country that follows these rules."
Your own totals, by calendar year and tax year
sellertotals adds up your sales from Vinted, eBay, Etsy, Depop and others. It counts sales and totals them per platform for each calendar year (the years platforms report on), and combines them for each tax year. That lets you set your own figures beside the copy a platform sends you. CSV exports are read in your browser for free. Screenshots or PDFs of your sales history use AI, and your first one is free. It doesn't decide whether you're trading or whether you need to tell HMRC. sellertotals isn't connected to any of these platforms or to HMRC.
This isn't tax advice. Check GOV.UK's guidance for sellers on digital platforms or an accountant for your situation, and check the figures before you submit anything.