My dad passed away a few weeks ago. My mum is still here, but she never had anything to do with running the house/ finances and doesn't have a clue about anything, she is very elderly and obviously very upset.
Dad worked all his life, mum never worked, so dad had a reasonable state pension, mum has a very basic one. No private pensions. Both have/had serious illnesses. Dad had higher rate attendance allowance, mum medium rate DLA. They were ok money wise but lived very frugally.
We are trying to work our way through dads filing to put affairs in order, changing things to mums name only etc.
During this we have found almost £12k in cash in their home. I don't know (but its possible/probable) if dad had this at home so bank balance was low enough for council tax rebate, or extra DLA, or less tax or ........I don't know anything about all these things as dad managed them all himself. From the paperwork found he was only getting a council tax reduction for being over 65. Can't see anything on anything else he has which implies savings in bank would have been an issue, would savings has impacted their AA or DLA?
No idea what to do now with this money.............scared to put in bank incase it opens a can of worms........what will bank ask if I walk in with £12k in notes!
Oh Dad! What were you doing! 
. Really don't need this worry just now as mums health is rapidly deteriorating too.