In the case of a beneficiary IRA distribution, the math for the required minimum distribution is complicated and can depend on the decedent's age, your own age, and the time since her death. The plan administrator should be able to tell you whether there was an RMD and the amount required. The amount of the RMD may also be accessible in your online account or paperwork you have received.
If your mother was receiving RMDs prior to her passing, you are also required to take RMDs from the inherited account. The amount you must take is a percentage of the total value of the account at the beginning of the year, determined by your age . Look up the life expectancy chart beginning on page 49 of this IRS publication using your age at the end of the year following your mother's death. Divide the account value at the beginning of the year by your life expectancy from the chart to determine the required minimum distribution. If your mother died prior to 2021, reduce your life expectancy by 1 for each year since her death. There is an example in the publication on page 12.
If your mother was not taking RMDs because she was younger than 70 1/2 if she died prior to January 1, 2020 or younger than 72 if she passed away after that, then you are also not required to take RMDs as long as you are withdrawing the entire balance within 10 years of the year of her passing.
If you were required to take an RMD, the easiest way is to call the administrator so they can tell you the RMD for 2021 if it is not available in any of your account information. They should be able to tell you the amount, and as long as your distribution was greater than that, you will not face any additional tax. Just enter in the amount of the RMD into TurboTax that the administrator tells you. If your distribution was not enough to cover the RMD, then the remaining amount that was not distributed is subject to penalties.
