[HELP] Vinted UK + HMRC notice

Hi everyone, hoping someone has been through this because I’m a bit lost.

Vinted sent me the HMRC notice for surpassing the £1,700 threshold this year. I went through the form and marked that I don’t have a National Insurance Number (even though I do, that was a mistake 🙃). After that, it just said “all set” and didn’t ask for anything else.

The thing is, I don’t make any profit from selling. Everything I sell is second-hand personal stuff I already owned. I’m selling roughly every two weeks because I’m decluttering my home.

Here’s the tricky part: even though everything is second-hand, I don’t have any way to prove it—no receipts, no photos of me using the items, nothing.

My main concern:

Could this affect my Universal Credit?

From what I’ve read, some people say any income matters, others say that if there’s no profit it doesn’t, and some mention self-employment… I’m honestly confused.

Some context: -Everything I sell is personal stuff I already owned -I always sell for less than I paid for it -It’s not a business -The NI number thing was a mistake, but I can’t seem to change it

Thanks in advance!