Final answer:
The term for the sale of a promissory note before maturity at a price less than the outstanding principal balance at the time of sale is a discount point.
Step-by-step explanation:
The term for the sale of a promissory note before maturity at a price less than the outstanding principal balance at the time of sale is called a discount point. It is an amount deducted in advance by a lender from the nominal principal of a loan as part of the borrower's cost of obtaining the loan.