For example in UK, you don't have to pay VAT if you make under 80.000 or something like that. But, you still have to register as a company or sole trader with H

For example in UK, you don't have to pay VAT if you make under 80.000 or something like that. But, you still have to register as a company or sole trader with HMRC and say that you are involved in an economic activity. And you still have to submit invoices. I doubt that any of these people send invoices through instagram messages...