In mortgages, the risk that a potential borrower (that is, a property buyer) will withdraw from the deal before it is finalized. Banking regulation requires that banks offering a given interest rate hold that rate for 60 days, during which the potential borrower is under no obligation to actually take out the mortgage loan. During that time, the bank usually makes preparations to sell the mortgage as a mortgage-backed security or as some other investment vehicle. If the potential borrower withdraws during those 60 days, the bank is exposed to the risk that it will lose out on the return it could have made from the MBS or other investment vehicle. Fallout risk is also called borrower fallout.