According to IRS Publication 537, "Transfer due to death. The transfer of an installment obligation (other than to a buyer) as a result of the death of the seller is not a disposition. Any unreported gain from the installment obligation is not treated as gross income to the decedent. No income is reported on the decedent's return due to the transfer. Whoever receives the installment obligation as a result of the seller's death is taxed on the installment payments the same as the seller would have been had the seller lived to receive the payments.
However, if an installment obligation is canceled, becomes unenforceable, or is transferred to the buyer because of the death of the holder of the obligation, it is a disposition. The estate must figure its gain or loss on the disposition. If the holder and the buyer were related, the FMV of the installment obligation is considered to be no less than its full face value. "
This would support Maribeth's statement that the "client 'steps into the shoes' of the decedent."