TBA-market transaction that sells one agency MBS position and buys a similar later-settling position.
A dollar roll is a TBA-market transaction that sells one agency MBS position and buys a similar position settling in a later month.
Dollar roll matters because it shows that mortgage-backed securities markets manage timing as well as price. Agency MBS participants may need to move exposure from one settlement month to another instead of simply buying or selling a security once.
It also matters for borrowers as a background concept. The borrower does not negotiate a dollar roll, but the liquidity and timing mechanics of the TBA market help support the rate sheets and lock-management systems that borrowers do experience.
Borrowers encounter dollar-roll effects only indirectly through the broader mortgage pricing environment.
The term becomes practical when explaining why lenders manage locked loans, expected closings, and investor delivery dates carefully. If loan production or settlement timing changes, the lender may need to adjust secondary-market positions.
| Term | What it explains |
|---|---|
| To-Be-Announced Market | Forward agency MBS trading channel |
| Dollar roll | Moving similar exposure from one settlement month to another |
| TBA Settlement | Completing a TBA trade with eligible pools |
| TBA Pair-Off | Offsetting a position rather than delivering as expected |
A market participant sells an agency MBS TBA position for one settlement month and buys a similar position for a later settlement month. The transaction changes timing exposure rather than representing a borrower-facing loan feature.
Dollar roll differs from TBA Settlement because settlement completes a trade, while a dollar roll moves similar exposure across settlement months.
It differs from TBA Pair-Off because a pair-off offsets a position, while a dollar roll replaces one timing position with another similar later position.
It also differs from Rate Lock because the rate lock is the borrower-facing promise, while dollar roll is a secondary-market timing transaction behind the scenes.