A Debt Security is an obligation that you owe another party, with the two parties agreeing on what the obligation will entail. It can be any form of debt, such as a mortgage, car loan, credit card or student loan.A debt security is a debt instrument that can be bought or sold between two parties and has basic terms defined, such as the notional amount (the amount borrowed), interest rate, and maturity and renewal date.A debt security is a debt instrument that can be bought or sold between two parties and has basic terms defined, such as the notional amount (the amount borrowed), interest rate, and maturity and renewal date. Debt securities are sometimes referred to as "securities."