Not really my business but i would think it would be wise to self assess and at least be in the system and pay something otherwise you are invisible and as someone suggested, this could get difficult later on. I am in a line of business where people think oh well you can take cash (a bit like the plumber mentioned above) but you know what ? I dont. Why? Because i like to present a genuine honest front to customers. I take most of my payments via mobile card reader now,,all above board.