A mortgage rate lock is a lender's written commitment to hold a specific interest rate and points for a set period — typically 30 to 60 days — while your loan is processed. If rates rise before closing, you keep the locked rate; if rates fall, you may need to pay a fee to renegotiate.
When you apply for a mortgage, the interest rate quoted at application is not guaranteed — it moves with the market daily. A rate lock is the mechanism that freezes your rate once you've found a home and chosen a lender. The CFPB describes a rate lock as a lender's written commitment to hold a specific rate and points for a defined period, so the terms don't change before closing.
Standard rate lock periods are 30, 45, or 60 days. Longer locks cost more — typically in the form of a higher rate or an upfront fee. If your closing is delayed beyond the lock expiration, you may have to pay an extension fee or re-lock at the current (possibly higher) market rate. Ask your lender what extensions cost before choosing a lock period.
Some lenders offer a float-down option: if rates drop by more than a specified amount after you lock, you can capture a lower rate once. Float-downs typically cost 0.5%–1% of the loan amount as an upfront fee. They make sense if rates are volatile and expected to fall. Not all lenders offer them, so ask explicitly during rate shopping.
Most borrowers lock once they are under contract on a home and have completed their lender selection. Locking too early (before a signed purchase agreement) wastes the lock window. Waiting too long risks rates rising before closing. The CFPB's Owning a Home rate checker helps you track real rate ranges so you can judge market timing.
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