I am very sorry for your loss.
Generally speaking, if his only income was Social Security, he probably didn't make enough money to be required to file a federal tax return. See the screenshot below for Filing Requirements for Most Taxpayers.
Prepare your father's income tax return just to make sure. If his taxable income is zero, don't file the income tax return.
- Simple returns (1040-EZ or 1040-A) with the standard deduction is supported in TurboTax Federal Free Edition.
- TurboTax Deluxe and higher versions are free if you do not print or e-file.