Prepayments penalties

Some lending institutions penalize borrowers who retire their loans early. In the United States, prepayment penalties are levied only for commercial mortgages, not for residential ones (both are penalized in the United Kingdom). Residential lenders, therefore, cannot be certain of the cash flows they will receive. This is known as prepayment risk. The uncertainty of mortgages cash flows, and the risk associated with it, is passed on to the securities backed by the loans. In this way, an MBS is similar to a callable bond, with the call exercisable at the discretion of the borrowers, and, as will be explained later, it can be valued using a similar pricing model. 

Flexible mortgages and cmrent account mortgages have the advantages for the borrower of being able to prepay without penalty and then. 

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