If you were the beneficiary of the plan, the plan custodian will send you a 1099R form by February 15. After that, just follow the instructions in TurboTax for a 1099-R. With most such plans, because your mother did not pay income tax on the contributions, you will owe income tax on the amount withdrawn or paid out.
in the unusual situation that your mother had named no beneficiaries for her retirement plan, the retirement income would have been paid to her estate, and you will need to file an estate tax return.
