Above posts moved from unrelated thread.
I'll have one more go, although why I'm doing so when it's like trying to explain Nietzsche to a shower curtain I have no idea.
Nobody is saying that people should put through expenses not connected to their job - that's tax evasion. What is a fact is that ANY expense which was incurred directly in the course of you doing your job can be put through, regardless of what you've bought/paid for or what your job is.
So if a punter asked you to paint him green and this required you to buy some paint and a paintbrush, these would be completely legitimate business expenses and would not require you to be registered as an artist or a painter and decorator, because that would be insane. Equally if I decided to do a one hour outcall to Aberdeen which would cost me double what I'd earn, I can put the travel costs through. But if you go to a gig in another town and decided to put your hotel and travel costs through on the sly that's not OK, (even if you work from hotels and put these through regularly) because you didn't book the hotel for work.
I can't simplify it any more that that. What I will say is that constantly posting anecdotes about people who are not here rather than actual first hand experience is getting tiresome - if all these friends want to contribute their experiences they can register and do so themselves.