Single-Family MBS
Creating a Single-Family Mortgage-Backed Security (“MBS”) starts when a bank or financial institution issues a mortgage loan to a borrower to help buy or refinance a home with one to four residential units. Fannie Mae buys loans from lenders and securitizes most of those loans into various security formats.
Single-Family MBS may be placed into other types of investment products with different features, such as Supers®, Fannie Megas®, Real Estate Mortgage Investment Conduits (REMICs), Stripped Mortgage-Backed Securities (SMBS), and other Structured Transactions.
Beginning June 3, 2019, as part of the Single Security initiative, we began issuing Uniform Mortgage-Backed Securities (UMBS®) for all to-be-announced ("TBA") -eligible securities backed by 30-, 20-, 15- and 10-year fixed-rate single-family mortgages. Additionally, all legacy TBA-eligible securities previously issued by Fannie Mae were automatically considered UMBS.
The Single Security initiative aims to ensure both Fannie Mae UMBS and Freddie Mac UMBS are fungible for deliveries into a single TBA market. In a TBA contract, the maturity, coupon, face value, price, and the settlement date of an MBS are known, but the issuer, be it Fannie Mae or Freddie Mac, and the actual unique security identifier are "to be announced" – i.e., not yet determined at the time the TBA contract is entered into.
More about Single-Family MBS
Single-Family MBS Overview
Learn about Fannie Mae's securitization of loans, MBS offerings, valuation considerations, and the availability of data and helpful resources.
HomeReady® Overview
Learn about Fannie Mae's affordable lending product, featuring innovative income flexibilities to help reduce barriers to homeownership.
Whole Loan Conduit Overview
Learn about Fannie Mae's Whole Loan Conduit, the lender approval process, benefits, and the availability of data and resources.
Why invest in Fannie Mae?
Fannie Mae MBS offer investors high-quality assets with attractive yields to fit various portfolio needs or investment strategies. Investors should exercise care to fully understand the value of any mortgage-backed investment and diligently review the applicable disclosure documents. Investors may want to work with their investment advisors to identify the potential risks versus rewards of investing in MBS.
Our Guaranty
Historically, MBS issued directly by Fannie Mae have not been rated by any major rating agency. However, on January 9, 2026, Moody’s Ratings (“Moody’s”) assigned a provisional (P)Aa1 senior secured shelf rating and a Aa1(cr) long-term Counterparty Risk Assessment to Fannie Mae, and also noted that Fannie Mae’s outlook remains stable. In its announcement, Moody’s noted that the “(P)Aa1 senior secured shelf rating is representative of the creditworthiness of Fannie Mae’s mortgage-backed securities (MBS) programs.” Standard & Poor’s and Fitch have not announced any similar ratings actions at this time.
In addition, it’s important to note that:
- Securities collateralized by Fannie Mae MBS are generally considered high quality, and senior tranches of such securities are often rated AAA, though ratings depend on the specific structure and issuer.
- Principal and interest payments on Fannie Mae-issued certificates are not guaranteed by the United States and do not constitute a debt or obligation of the United States or any of its agencies or instrumentalities other than Fannie Mae.
- Fannie Mae uses prudent underwriting guidelines to evaluate the credit quality of the loans it guarantees to minimize losses to its investors.
Quick Securities Locator
Search for disclosure and related documents for a security. Search by:
- Security Identifier (e.g., BD3584)
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