Selling on eBay taxes?

I think eBay has a rule that you have to pay tax and apply as a self employeed person once you sell up to 1000 pounds. Is this true? I am on governmental payment since I am an immigrant with no job (I only have a BRP card). Will my paycheck from the government be removed once I apply as self-employed?

Hi,

Please refer to:

 Selling online and paying taxes - information sheet

Thank you.