Fannie Mae Selling Guide Chapter C3-6: Pooling Loans into Fannie Majors
Lenders can pool mortgages into two types of MBS, which includes UMBS:
Fannie Mae publishes the full text of this section: Fannie Mae Single Family Selling Guide on the Fannie Mae website. Zeitro Strata answers questions about it with the passage and page cited.
Guideline text quoted as published by the agency. The latest published version governs. This is not an underwriting decision.