A large amount of theoretical research has been conducted concerning the impact of debt instrument features such as callability, tax treatment, and default risk upon valuation and yield. Almost all this research has been performed on bond-like instruments; this is unfortunate since a large proportion of debt instruments is amortizing. This research develops a model for the spread between bonds and amortizing instruments with otherwise identical features. The shape of the term structure is crucial. Furthermore, the behavior of the spread is systematically related to the level of interest rates, tax rates, degree of default risk, and maturity where the maturity relation changes sign at intermediate maturities.