What Is a Z-Bond?

What Is a Z-Bond?

By Charles Joseph | Editor, Financial Affairs
Reviewed by Corey Michael | Senior Financial Analyst

A Z-Bond, or an accrual bond, is a unique type of bond commonly found within a collateralized mortgage obligation (CMO).

Unlike regular bonds that make periodic interest payments, Z-Bonds do not pay periodic interest and accrue its interest instead.

When we discuss a collateralized mortgage obligation, we’re referring to an investment vehicle where multiple mortgage-backed securities are bundled together and grouped into various risk categories known as “tranches.”

There are several types of bonds within these tranches, with Z-Bonds being a particular category.

Z-Bonds are positioned as the last tranche in a CMO.

They are typically issued with no scheduled principal or interest payments while other tranches within the CMO are still active.

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The reason behind this method is that the unpaid interest contributes to the accumulation of other tranches, thereby shielding investors in higher-tier tranches from default risks.

Once the other tranches in the CMO are retired, the Z-Bond will convert into a regular bond, called an Amortizing Principal Bond.

At this point, it will start to receive both principal and interest payments as scheduled, benefiting from the previously accrued interest.

Thus, Z-Bonds offer risk-tolerant investors a potentially lucrative long-term investment, as long as the CMO performs well and the early tranches of securities within the CMO are successfully repaid.


A Z-Bond may cater to investors who are looking for long-term investments with potentially higher returns while contemplating the intricacies of collateralized mortgage obligations.

Key Takeaways

  • A Z-Bond, also known as an accrual bond, is a type of bond found within a collateralized mortgage obligation (CMO).
  • Unlike regular bonds with periodic interest payments, Z-Bonds gather interest without making immediate payments – instead, they accrue the interest.
  • Z-Bonds belong to the last tranche of a CMO structure, receiving no principal or interest payments during the time the other tranches are still active.
  • Accrued interest from Z-Bonds contributes to the growth of active tranches and provides protection to investors in higher-tier tranches against default risks.
  • Once other tranches are paid off, Z-Bonds convert into regular, Amortizing Principal Bonds, which receive both principal and interest payments until they reach maturity.
  • Z-Bonds suit investors who are focused on long-term investments with higher returns and are considering the risk involved with collateralized mortgage obligations.

Related Questions

1. What are Z-bonds in the context of collateralized mortgage obligations (CMOs)?

Z-bonds, also known as accretion bonds or accrual bonds, are a type of bond in CMOs that do not pay interest until all the other tranches are paid off. Instead, the interest that would have been paid accrues and increases the face value of the bond.

2. When do Z-bonds begin to pay interest?

Z-bonds start paying interest only after all the other tranches in the CMO have been retired. Until then, the interest is added to the principal of the bond, increasing its face value.

3. Why would an investor choose a Z-bond over other types of bonds?

An investor may choose a Z-bond for the potential of a larger payout in the future as the bond’s face value increases over time due to the accrued interest. They are a type of long-term investment that could be attractive for investors with a long time horizon who seek higher yields.

4. What is the risk associated with investing in Z-bonds?

The main risk of Z-bonds is their long maturity and deferment of interest payments. This makes them more exposed to interest rate risk. If interest rates rise significantly during the accrual period, the value of the Z-bonds could decline. Moreover, because they don’t make regular interest payments, they may not be suitable for investors who require regular income.

5. How does the “Z” in Z-bond come about?

The “Z” in Z-bond is derived from the term “zero-coupon bond,” which is a bond that does not pay periodic interest. Although Z-bonds eventually do pay interest after the other tranches are retired, they function as zero-coupon bonds during the accrual period.