My father passed away in March 2010 without a will or estate. I just received a letter from the IRS addressed to my Dad stating that he owed $2500 for the year 2010. To my knowledge tax forms were not submitted for the year 2010. My father received a small amount each month from SS and he had a government pension. He also had small interest payments. The total for the year in question was less then 10,000. My Dad was 92 and legally blind. Do I respond to this letter or return it marked Deceased?