What is the maximum income you can earn, before expenses are taken off, before you have to start paying tax. Also, what is the maximum profit you can earn before you have to pay tax.
Individuals under 65 years old currently have a 'personal allowance' of £6475 per year. If you earn no more than that in a year you'll pay no tax. Thereafter 20p out of every £1 you earn goes to the tax man. (If you earn more than £43875 per year you then start losing 40p out of every £1 thereafter).
There's no maximum you can earn BEFORE expenses are taken off to start paying tax. You could conceivable "earn" £10 million per annum but if your expenses are £9.995 million then you'd pay no tax.