Payroll question

[chlodah]

Random story but I helped a 90 year old man I know, on a voluntary basis run his hardware shop whilst he was in hospital for several months. He wants to write me a cheque as payment but what would be the tax implications of this be? Would I have to do a tax return where you submit all your yearly invoices (which I don’t have) or can I just make a declaration to HMRC and pay 20% direct to them as this would be secondary employment? Also implications of him in terms of pension, paye etc? Clueless! Thank you