If the 1099R was received prior to death, her SSN should be on it and it is reported on her final 1040. If your or other beneficiary name is on it and their SSN it is reported on their return. There is no stepped-up basis on retriment accounts. There is one 3rd scenario, if paid to the Estate then a 1041 (Estate return) would report and pay the tax on the 1041.
