Thanks, @AshgarMary. I tend to take the view that I tell the tax man about my income and he/she can decide what that means in tax terms. I do all my tutoring at home, so my expenses are minimal and it would be far better for me to get the tax relief on £1,000 than relief on expenses. I found a little about it via Google - I am sure that there will be a lot more over the next year. It won't change how I organise my tutoring, so I won't need to do anything about it until I do my 2017-2018 tax return.