Hi boardmember,
Please accept my sincere condolences on the loss of your young wife.
As soon as you are able you should advise Revenue, which as others have said, will be very sympathetic.
You would be entitled to the Widowed Person’s tax credit in the year of bereavement, currently, 3,300. You are entitled to this irrespective of the basis on which you and your late wife were assessed.
If you have a child or children, you would also be entitled to an additional credit for 5 years starting from 2016. This is in addition to the Single Person Child Carer credit.
Regrettably, you cannot claim joint assessment retrospectively.