The Form 1099-R that you received for this distribution will include code 4 in box 7 to indicate that the distribution a distribution to the beneficiary of the deceased. Enter the Form 1099-R that you received for this distribution under Wages & Income -> Retirement Plans and Social Security -> IRA, 401(k), Pension Plan Withdrawals (1099-R), then answer the follow-up questions, including indicating how much of the distribution was RMD. Later, click the Continue button on the Your 1099-R Entries page and, if true, indicate that you received all of the RMD of this account.
