New Enterprise Allowance - taxable or not?

A new client has been receiving New Enterprise Allowance. Please can someone tell me (with authority for the answer) whether it is taxable or not. Depending on who I ask and where I look, the answer is different. Gov.uk says that 'any money you get does not affect income tax' implying that it is tax-free.  However, BIM40401 says that it is business income - how then can it not affect income tax? Which is correct please?