Thanks for your question- I am Sam and I am one of the UK tax experts here on Just Answer.
Did this payment come to you directly or through your late brothers estate - have you a solicitor handling your brothers estate?
As all of the monies or assets he holds will just need to be reviewed for Inheritance tax - if as yet you have done nothing then you should go through the advsie on the Gov website link here
If your brother was working it may well be he is owed tax overpaid - so its often best to get a solicitor to mange everything in one place and ensure all the relevant legal aspects are undertaken as if any tax is due on these amounts its not on you but the estate to pay.
Let me know if I can assist further - I am due to head out to client meetings soon but will be back later this afternoon/early evening if you have any follow up questions