In the year in which a spouse dies, you are still a married couple as far as the IRS and your state Comptroller of the Treasury are concerned. Ergo, you may file jointly. My husband died in January 2006. When I filed my income tax returns for the calendar year 2006 in April of 2007, I filed married filing jointly. Next to his name I wrote in: DECEASED.
I gather that had we, for some reason such as being filthy rich (ha!), been in the habit of filing separate returns, his would have been filed as ESTATE OF JOHN DOE (not his name, obviously).
So I did not change our joint account with the bank to just my name until after those refunds came in. I TOLD the bank right from the git go that he was dead, but did NOT change the accounts. After the refunds and when I was, paperwork wise, all single, I did the paperwork removing his name.