Refunded bonds, which are a subset of the municipal and corporate bond classes, are bonds that have their principal cash amount already held aside by the original issuer of the debt. This is often accomplished through the use of a sinking fund, an account a firm uses to set aside money earmarked to pay off the debt from a bond or other debt issue. The sinking fund gives bond investors an added element of security.
A refunded bond should not be confused with a pre-refunding bond, which is a debt security that is issued in order to fund a callable bond. With a pre-refunding bond, the issuer decides to exercise its right to buy its bonds back before the scheduled maturity date.
Refunded bonds are low-risk investments because the principal amount is already accounted for. The funds required to pay off refunded bonds are held in escrow until the maturity date, usually by purchasing Treasury or agency paper. Refunded bonds can also be referred to as pre-refunded bonds or prior issues.