Code Sec. 453(d) allows an election out of the installment sale method and (d)(2) says that the election has to be made on or before the due date for filing the return and then (d)(3) says the election is revocable only with the consent of the Secretary of the Treasury-------- the IRS. So, your father made the election which is now only revocable with consent of the IRS if you want to take it that far. Entering on the estate return and making distributions would be easier and save tax dollars versus having the estate pay the taxes on the gain and interest.
