Commercial mortgage-backed security

Commercial mortgage-backed securities (CMBS) are a type of mortgage-backed security backed by commercial mortgages rather than residential real estate. CMBS tend to be more complex and volatile than residential mortgage-backed securities due to the unique nature of the underlying property assets.

CMBS issues are usually structured as multiple tranches, similar to collateralized mortgage obligations (CMO), rather than typical residential "passthroughs." The typical structure for the securitization of commercial real estate loans is a real estate mortgage investment conduit (REMIC), a creation of the tax law that allows the trust to be a pass-through entity which is not subject to tax at the trust level.

Many American CMBSs carry less prepayment risk than other MBS types, thanks to the structure of commercial mortgages. Commercial mortgages often contain lockout provisions after which they can be subject to defeasance, yield maintenance and prepayment penalties to protect bondholders. European CMBS issues typically have less prepayment protection. Interest on the bonds may be a fixed rate or a floating rate, i.e. based on a benchmark (like LIBOR/EURIBOR) plus a spread.

The following is a descriptive passage from the "Borrower Guide to CMBS" published by the Commercial Mortgage Securities Association and the Mortgage Banker's Association:

Commercial real estate first mortgage debt is generally broken down into two basic categories: (1) loans to be securitized ("CMBS loans") and (2) portfolio loans. Portfolio loans are originated by a lender and held on its balance sheet through maturity.

In a CMBS transaction, many single mortgage loans of varying size, property type and location are pooled and transferred to a trust. The trust issues a series of bonds that may vary in yield, duration and payment priority. Nationally recognized rating agencies then assign credit ratings to the various bond classes ranging from investment grade (AAA/Aaa through BBB-/Baa3) to below investment grade (BB+/Ba1 through B-/B3) and an unrated class which is subordinate to the lowest rated bond class.

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