• The 48 Hour Rule refers to the part of the mortgage allocation process related to the purchase and sale of Mortgage Backed Securities (MBS) to be announced (TBA).

  • The 48 hour rule stipulates that the MBS seller notifies the buyer of the details of the underlying mortgages that make up the MBS by 3:00 pm. Eastern time, 48 hours before the settlement date.
  • The Securities Industry and Financial Markets Association (SIFMA) applies the 48 hour rule.
  • When MBS are traded on the secondary market, the underlying mortgages are unknown, which helps facilitate trading and liquidity.
  • Certain information is negotiated when making a transaction with MBS, such as price, denomination and coupon, but not the underlying mortgages.
  • The TBA market is the second most traded secondary market after the US Treasury market.