I work full-time in the NHS and I've been asked by one of our consultants if I can help out with a project he and a group of his colleagues are working on. I would do the work in my own time, be paid an agreed monthly sum and it is something that would be potentially long-term. Does anyone know what the tax arrangements are for doing something like this? Would I be self-employed and have to do tax returns etc? Any advice would be greatly appreciated.