What it means
Mortgage lenders live in the gap between two promises. To a borrower, the lender commits to fund a loan at a locked rate weeks before closing, and to sleep at night the lender obtains a matching commitment from an investor to purchase that loan on similar terms.
The pairing of the two is a back-to-back commitment. The structure manages interest-rate risk, not credit risk.
Between rate lock and loan sale, market rates move, and an unhedged pipeline of locked loans can lose value fast, so the forward commitment from the investor fixes the exit price and transfers the market risk to whoever stands on the other side. The structure predates modern hedging tools, since before deep derivatives markets matched commitments were the only way to lock an exit price, and a lender might instead sell futures or agree to a forward sale, with the choice turning on cost, accounting, and counterparty access.
Supervisors watch the practice closely because the hedge is never perfect. The Comptroller's Handbook on mortgage banking describes how mandatory forward sales commitments interact with fallout, the share of locked loans that never close, and when fallout rises the lender may have committed to deliver more loans than it originates, forcing it to buy loans in the market to meet its commitments.
Commitments also come in flavours that price differently, as a mandatory forward sale commits the lender to deliver or pay a penalty while best-efforts arrangements pass the fallout risk back to the investor, so the pairing works cleanly only when the terms on both sides mirror each other. For borrowers, none of this machinery is visible, yet it shapes the price they pay.
The rate lock a bank offers for free is possible precisely because the bank can lay the risk off through the second commitment, and the cost of that protection lives inside the quoted rate. Secondary-market investors shape the terms available, since the price of a forward commitment moves with demand for mortgage securities, so the borrower's rate lock quietly reflects conditions in capital markets far from the high street.
Finance teams managing a pipeline treat the two commitment books as one system. Locked loans sit on one side, forward sales on the other, and a daily measure of the mismatch in between, because the mismatch is where the profit leaks.
Small lenders can rent the capability through correspondent and wholesale channels, where a local lender offers locked rates while a larger institution supplies the forward side, spreading the back-to-back structure through the whole market. The same paired-commitment logic appears wherever an intermediary both buys and sells forward, from trade finance to commodity dealing.
That makes the mortgage version a template worth recognising. Anyone who sees a business promising a customer a fixed price while it separately arranges its own supply price is looking at the same idea.
In practice
Real-world examples.
Example
A mortgage lender locks a borrower at 6.5% for forty-five days and, the same day, agrees to sell the loan to an investor at a fixed price. When the loan closes, it delivers it and earns the agreed margin. A rise in rates in between does not hurt the lender.
Example
A trade finance intermediary promises an importer a shipment at a fixed price and simultaneously signs a purchase contract with the exporter at a lower fixed price. The difference of $12 per unit on 5,000 units is a locked margin of $60,000. The intermediary's risk is mainly that one side defaults.
Example
A wholesale commodity dealer agrees to deliver grain to a food manufacturer in three months at a fixed price and buys the same quantity forward from a farmer's cooperative. Market price swings in the meantime do not change its margin. It monitors the cooperative's ability to deliver, since a missed delivery would leave it exposed.
Formula
Calculation
Unhedged shortfall = forward sales committed - loans actually closed
Fallout = locked loans that do not close / locked loans x 100
Worked example (illustrative): a lender has $10,000,000 of locked loans and sells $10,000,000 forward to an investor at a price of 101.00 (that is, $101 per $100 of loan).
Suppose 20% of the locks fall out: fallout = 20%, so loans closed = $10,000,000 x 80% = $8,000,000.
Shortfall = $10,000,000 - $8,000,000 = $2,000,000 of loans the lender has promised but does not have.
If rates fell, which is when borrowers tend to walk away, and the market price rises to 103.00, the lender must buy $2,000,000 of loans at 103 to deliver at 101.
Loss = ($103 - $101) / $100 x $2,000,000 = 2% x $2,000,000 = $40,000.
The price and fallout figures are assumptions chosen to show how a mismatch creates a loss.Case study
Seen in the real world.
Fictional example. A small lender, an invented firm called Harbourside Mortgage, locks rates for borrowers up to sixty days ahead and sells every locked loan forward to a larger investor. The pipeline looked perfectly hedged until a drop in rates led many borrowers to walk away and refinance elsewhere. Fallout reached 30%, so Harbourside held forward sales it could not fill and had to buy loans at higher prices to deliver.
Finance reported the loss as an exception and began tracking fallout daily by loan type. It later shifted part of its volume to best-efforts commitments and hedged only the share of the pipeline it expected to close. The lender also priced the risk into its rate sheet, because the free lock had a cost. It added a small fee for longer lock periods, which reduced its exposure to fallout.
Watch out
Common mistakes.
- Treating the pairing as a perfect hedge. Fallout can leave the lender short of loans, and the mismatch can cost real money.
- Confusing it with credit protection. The structure manages interest-rate risk, and the borrower can still default after the loan is sold or held.
- Assuming all commitments have the same terms. Mandatory and best-efforts forward sales put the fallout risk on different parties.
Questions
People also ask.
What is a back-to-back commitment?
A lender's promise to fund a loan at a locked rate, paired with an investor's promise to buy that loan on similar terms.
Why do lenders use it?
To fix the exit price of a loan between rate lock and sale, which removes most of the interest-rate risk from the pipeline.
Who bears the risk if a locked loan never closes?
In a mandatory forward sale the lender, who may have to pay a penalty or buy loans elsewhere, and in a best-efforts arrangement the investor.
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