A Real Estate Mortgage Investment Conduit (REMIC) is a type of multiclass mortgage-related security in which interest and principal payments from the mortgage-related assets serving as collateral are structured into separately traded securities called classes. The cash flow from the underlying collateral is directed to several classes, which may have different coupon rates, average lives, prepayment sensitivities, and final maturities. REMICs further enhance the mortgage securities market with their increased efficiency.
A grantor trust is a pass-through vehicle that, like a REMIC, issues separately traded classes. However, grantor trusts are treated differently than REMICs for federal income tax purposes, and, unlike a REMIC, the classes in grantor trusts cannot be "time tranched." This means each grantor trust class must receive its proportionate share of principal from the underlying collateral each month until such collateral is paid off. Each holder of a grantor trust certificate is treated for tax purposes as owning an undivided interest in the underlying collateral. The mortgage-related assets serving as collateral and providing the cash flow for Fannie Mae grantor trusts are specifically described in the trust's disclosure documents.