A special type of bond class in a sequential pay collateralized mortgage obligation. This class of bond does not receive any interest or principal payments until all other tranches have been completely paid off. In a Z-tranche, the interest that is not paid is accrued and added to the principal for future interest calculation purposes.  

|||The main purpose of the Z-tranche is to speed up the maturity of the senior tranches by disbursing payment that the Z-tranche was suppose to receive to the higher priority tranches. Investors that possess long-term liabilities or those who worry about reinvestment risk would benefit from investing in a Z-tranche bond.