Rate Lock
A lender's commitment that your interest rate won't change between the offer and closing, as long as you close within the lock period and your application doesn't change.
Last updated: October 3, 2026Mortgage rates can change daily, sometimes hourly. A rate lock freezes yours between the offer and closing, provided you close within the stated window and nothing material in your application changes. Locks are typically available for 30, 45 or 60 days, and sometimes longer. Some lenders lock as part of issuing the Loan Estimate and some don’t; the top of page 1 tells you whether you’re locked and until when.
A lock is not unconditional. Your rate can still move if you change the loan type or down payment, the appraisal comes in higher or lower than expected, your credit score changes (say, because you financed a sofa mid-process), or the lender can’t document bonus or overtime income. Locks also cut both ways: if rates fall after you lock, you may be stuck with the higher one. And extending an expiring lock can be expensive. Rate-lock fees, where charged, appear in the origination charges on the Loan Estimate.
The NYC wrinkle is timing. A co-op purchase has a board approval step between contract and closing that you don’t control, so ask your lender how long the lock runs, what an extension costs, and what happens if closing slips, before you pick the lock length.
Worked example
On a $600,000, 30-year loan locked at this site’s default 6.95% rate, principal and interest is about $3,971.69 a month. If rates hypothetically climbed to 7.20% before closing and you hadn’t locked, the payment would be about $4,072.73, roughly $101 more a month, or about $1,212 a year, for the life of the loan unless you refinanced. That’s the risk a lock takes off the table; the trade-off is that you don’t get the lower payment if rates fall instead.
Model how a quarter-point swing changes what you can afford on the Rate Sensitivity tool.