If you don't take the required minimum distributions from your account, you will be subject to a penalty equal to 50% of the amount that should have been withdrawn. You must withdraw all assets from the inherited IRA within 10 years. As long as the account is depleted within this time-frame, the RMD penalties can generally be avoided.
TurboTax asks how much of this payment was a RMD? All, part, or none? Is it even an RMD being that he is deceased?
The RMD is based on your father's age at the time of death. If you received a payout for the account, you received the RMD because there is nothing left in the account. If you only took a partial distribution, you can ask the plan administrator (the person/ company you received the 1099-R from).
Required Minimum Distributions (RMDs) generally are minimum amounts that a retirement plan account owner must withdraw annually starting with the year that he or she reaches 72 (70 ½ if you reach 70 ½ before January 1, 2020), if later, the year in which he or she retires.