No. Getting preapproved for a mortgage does not lock in your interest rate. The rate printed on a preapproval letter is an estimate tied to market conditions and your credit profile on the day the lender ran your file, and it can move up or down every day until you formally lock. Most lenders won’t let you lock at all until you have a signed purchase agreement on a specific home.
Why the Preapproval Rate Is Only an Estimate
A preapproval letter confirms that you meet a lender’s basic underwriting guidelines for a certain loan amount and program. The rate quoted alongside it reflects pricing on that particular day for the program you’d likely qualify for. It’s not a commitment and not a promise.
The lender can’t commit to a price because no property has been identified, no appraisal has been ordered, and no final loan terms have been set. Federal disclosure rules require lenders to give accurate estimates, but those estimates can be revised when circumstances change, which they almost always do during a home search stretched over weeks or months.1Consumer Financial Protection Bureau. TILA-RESPA Integrated Disclosure FAQs
When You Can Actually Lock the Rate
You can lock your interest rate once you have a signed purchase agreement on a specific home and have submitted a formal loan application. The lender needs a real property address, a purchase price, and a defined loan amount before it will commit to holding a rate. Without those details, it has no way to hedge the rate in the bond market, and it won’t take on the risk of guaranteeing one.2Consumer Financial Protection Bureau. What’s a Lock-In or a Rate Lock on a Mortgage
The lock usually happens either when your loan application is submitted or shortly after underwriting begins. Some lenders lock automatically when they issue the initial Loan Estimate; others wait for you to ask.2Consumer Financial Protection Bureau. What’s a Lock-In or a Rate Lock on a Mortgage Don’t assume yours is locked because you applied. Ask your loan officer to confirm in writing.
To lock, the lender needs the property address, the loan amount, the loan program (30-year fixed, 15-year fixed, ARM), the lock duration you want (commonly 30 to 60 days, sometimes up to 120), and any discount points you’re paying.3Federal Reserve Board. A Consumer’s Guide to Mortgage Lock-Ins Rates also differ depending on whether your loan falls within the conforming limit, which is $832,750 for a single-family home in most areas in 2026, or crosses into jumbo territory.4FHFA. FHFA Announces Conforming Loan Limit Values for 2026
Lock-and-Shop: The Narrow Exception
A small but growing number of lenders offer “lock-and-shop” programs that let you secure a rate before you’ve identified a property. These programs typically lock for 90 to 120 days and require you to get a home under contract within a set window. They usually charge an upfront fee and may be limited to conventional, FHA, or VA loans within conforming limits.
Lock-and-shop products often include a one-time float-down, so if rates drop meaningfully during your search you can adjust downward once. These arrangements can make sense when rates are volatile and you expect a long search, but the upfront fee doesn’t always pay for itself if rates hold steady or fall on their own.
What Can Move Your Rate Between Preapproval and Lock
Two forces push the number around between preapproval and lock: the market, and your own finances.
Market Movement
Mortgage rates track the yield on 10-year Treasury notes far more closely than they track the Federal Reserve’s short-term federal funds rate.5Fannie Mae. What Determines the Rate on a 30-Year Mortgage Inflation data, jobs reports, and shifting expectations about growth can push yields, and mortgage rates with them, several times in a single day. A rate quoted on Monday morning may no longer exist by Monday afternoon. There have also been periods when the Fed cut short-term rates and mortgage rates climbed anyway, so don’t wait to lock because you’re expecting a Fed meeting to bring rates down.
Your Credit and Debt
Your finances at the moment you lock determine which pricing tier you land in. New debt taken on since preapproval, a car loan or a large credit card balance, raises your debt-to-income ratio and can push you into a higher rate than the letter suggested. Lenders recalculate at the lock and again before closing.
A credit score drop matters too. Fannie Mae’s loan-level price adjustments create steep cost differences across score and loan-to-value brackets. On a loan above 75% LTV, the pricing adjustment for a borrower with a 740 credit score is 0.875%, while a borrower at 700 pays 1.375%, half a percentage point in extra fees for a 40-point score difference.6Fannie Mae. Loan-Level Price Adjustment Matrix Lenders using risk-based pricing must notify borrowers when their credit places them in a less favorable tier.7Consumer Financial Protection Bureau. 12 CFR Part 1022 Regulation V – Section 1022.72 General Requirements for Risk-Based Pricing Notices
Loan-to-Value Shifts
If the home appraises for less than the purchase price, or you reduce your down payment, your loan-to-value ratio climbs. A higher LTV exposes the lender to more risk, and that translates to a higher rate. A borrower putting 10% down will generally receive a worse rate than one putting 20% down.8Consumer Financial Protection Bureau. What Is a Loan-to-Value Ratio and How Does It Relate to My Costs When these material changes hit after the initial Loan Estimate, the lender must send revised disclosures with the updated terms.9Federal Register. Amendments to Federal Mortgage Disclosure Requirements Under the Truth in Lending Act Regulation Z
What the Lock Costs and What You Get
Many lenders offer 30- to 45-day locks at no separate charge, with the cost baked into the rate itself. Longer periods of 60 or 90 days usually carry an explicit fee because the lender bears more market risk holding a rate that long. Fees for longer locks generally run from 0.25% to 0.50% of the loan amount.3Federal Reserve Board. A Consumer’s Guide to Mortgage Lock-Ins
Some lenders charge lock fees upfront and may not refund them if the loan doesn’t close, whether you cancel or your credit is denied.3Federal Reserve Board. A Consumer’s Guide to Mortgage Lock-Ins Others fold the cost into closing. Before you lock, ask specifically whether there’s a fee, when it’s charged, and under what circumstances you’d get it back.
Once you lock, you should receive a rate lock agreement spelling out the interest rate, any points or lender credits, and the exact expiration date. If your initial Loan Estimate went out before the lock, federal rules require the lender to send a revised Loan Estimate within three business days reflecting the locked rate.10eCFR. 12 CFR 1026.19 Certain Mortgage and Variable-Rate Transactions Check that the rate matches what you agreed to, the property address is right, and the expiration gives you enough time to close.
The lock runs both ways. The lender can’t raise your rate while it’s in force, and you can’t demand a lower one if the market drops, unless you have a float-down. If you walk away from the property or miss the deadline, the lock simply expires. Points paid to buy down the rate are fixed at the lock and appear on both the Loan Estimate and Closing Disclosure; by law they must correspond to a discounted interest rate.11Consumer Financial Protection Bureau. How Should I Use Lender Credits and Points (Also Called Discount Points)
Float-Down Options
A float-down lets you adjust your locked rate downward if market rates fall by a set margin before closing. Most provisions only trigger if rates drop meaningfully below your locked rate, often a quarter to half a percentage point. Some lenders include the feature free; others charge a separate fee. Either way, you can usually exercise it only once, and you have to ask for it up front, since it won’t appear automatically in your lock.
The math is straightforward. If the float-down fee is 0.25% of a $400,000 loan, that’s $1,000. Rates need to drop enough that your monthly savings over the life of the loan exceed the upfront cost. A small drop may save less over 30 years than you paid for the option.
If the Lock Expires Before You Close
If closing gets delayed past your lock’s expiration, the lender will typically offer two choices: extend the lock or let it lapse and reprice your loan at the market rate that day.
Extensions usually run in 15-day increments at 0.125% to 0.25% of the loan amount each, and most lenders cap the number of extensions at around three. Those fees add up quickly on a large loan, so build a buffer into your original lock period rather than cutting it close. Appraisal holdups and title issues are more common than most buyers expect.
Letting the lock expire is a gamble. If rates dropped, you may come out ahead. If they rose, you’re stuck with a higher payment for the life of the loan. Pick a lock period that comfortably covers your expected closing timeline, with room for the delays that tend to show up in the last two weeks.