obligation

CDOs are described as structured asset-backed securities because they pay cash flows to investors in a prescribed sequence, based on how much cash flow is collected from the package of assets owned.

The CDO is split into different risk classes known as tranches. Interest and principal payments are made in order of seniority so that senior tranches have the least risk. Junior tranches, which have higher default risk, usually have higher coupon payments.

A typical CDO may consist of a portfolio of 100 corporate bonds and have an average S&P rating of B+. Assuming a total portfolio size of $300 million, the CDO might have six classes or tranches:

The Class A senior tranche will offer investors the lowest yield since it has the highest S&P rating. The equity tranche would have the highest yield since it is the most risky component of the deal structure.

When an investor purchases a CMO, he or she purchases some class or tranche of the security whose risk depends on the maturity structure of the mortgages backing it. These tranches are usually designated as A, B, C, etc. and increase in degree of risk as the letters ascend.

To illustrate, Class A of a CMO would be the highest risk tranche offering the highest rate of return based on mortgages that still have a long term until full repayment by the borrowers. For this reason, they are exposed not only to interest rate and default risk but also to prepayment risk, the risk that borrowers will pay off the mortgage in advance of the mortgage term (e.g. 15 years, 30 years, etc.). Class A in this CMO will be the first of all of the tranches to absorb losses from borrowers' failure to make payments. Class A will, however, also be the first to receive money from prepayments.

By contrast, Class C of a CMO would carry the least risk for the holder, but offer a much lower rate of return. This is because the mortgages backing it are likely approaching their full repayment, meaning that the holder is solely receiving interest, and perhaps some principal payments from the remainder of the mortgage term. For this reason, Class C CMOs will receive little or no returns from prepayments.

A borrower, for example, has an obligation to make payments of an agreed-upon size on an agreed-upon date. A company may have an obligation to provide certain disclosure to the Securities and Exchange Commission (SEC). A board may have an obligation to pay an executive a certain amount of money if certain events occur, and a lender may have an obligation to charge a certain amount of loan interest for a fixed period of time, even if it can get a higher interest rate later on other loans.