The yield spread for a given issuer that is added to the yield for the corresponding maturity of the on-the-run Treasury issue. For example, if the yield spread for issuer XYZ is 1.4% for a maturity of 10 years, and a 10-year yield for an on-the-run Treasury issue is 4.6%, then the issuer’ on-the-run yield would be 6%.

As with Treasury issues, a yield curve can be inferred for every issuer. Typically, the yield spread increases with maturity (the longer, the higher; the shorter, the lower).