Hello Frederick, I'm Keith and happy to help you with your question. I am so sorry to hear of your wife's demise.What you need to do is claim the correct Personal Allowance for your age and also possibly Married Coulples Alowance for the period when your wife was with us.
Here is the HMRC advice on the subject:
'You can claim Married Couple's Allowance if you're married or in a civil partnership and at least one spouse or civil partner was born before 6 April 1935.
It's an amount that is taken off your tax bill - so you can only claim it if you pay tax. However, if your income isn't high enough to benefit from the allowance you can transfer the surplus to your spouse or civil partner.'
Personally, I would advise you to take this up in writing, rather than spend a frustrating time waiting for HMRC to answer. This has been the subject of adverse complaints in the press and comments in Parliament. Also in writing there can be no confusion and less chance of someone getting hold of the wrong end of the stick, that is if they can even find the stick at all!.