Yes, your interest rate can change after pre-approval, and it often does. A pre-approval letter shows what a lender was willing to offer on the day it ran your numbers, not a locked-in loan commitment. Until you formally lock a rate on a specific property, the number on that letter floats with the market and with any changes to your finances.
Why Pre-Approval Doesn’t Fix Your Rate
A pre-approval letter tells sellers you have the financial backing to make a serious offer. It doesn’t obligate the lender to fund a loan at the quoted rate. That rate reflects the pricing available to a borrower with your credit score, income, and debt load on the day the lender pulled the file. Change any of those inputs, or wait long enough for the market to move, and the pricing changes with them.
Most pre-approval letters expire after 60 to 90 days. Once that window closes, you reapply with updated documents and a fresh credit check, and the new rate reflects current conditions. Even within the window, the rate keeps floating until you take a specific step to freeze it through a rate lock, which only becomes available once you have a property under contract.
What Makes the Rate Move
The Bond Market
The biggest driver of day-to-day rate changes is outside your control. Lenders price 30-year fixed mortgages by adding a spread on top of the yield on the 10-year Treasury note, because the average mortgage gets paid off or refinanced in roughly seven to ten years and the 10-year Treasury is the closest-duration benchmark.1Fannie Mae. What Determines the Rate on a 30-Year Mortgage When Treasury yields rise, mortgage rates follow. When yields fall, rates tend to ease.
Inflation reports like the Consumer Price Index, Federal Reserve decisions on the federal funds rate, employment data, geopolitical events, and shifts in investor appetite for mortgage-backed securities all push yields around. A rate that looks attractive on Monday can move a quarter point by Friday.
Changes to Your Own Finances
Lenders almost universally pull your credit a second time shortly before closing. Federal rules require them to evaluate at least eight factors before approving a mortgage, including current income, employment status, existing debts, and credit history.2eCFR. 12 CFR 1026.43 – Minimum Standards for Transactions Secured by a Dwelling If any of those shifts meaningfully, the lender recalculates.
Modest changes matter. A single late payment that drops your score 20 or 30 points can bump you into a worse pricing tier. Financing a car or furniture raises your debt-to-income ratio. Switching employers, moving from salaried to commission-based income, or cutting your hours can force the lender to reassess whether you can handle the monthly payment. A higher rate is the optimistic outcome; sometimes the lender rescinds the approval entirely.
The Property You Choose
Your pre-approval rate is calculated before you pick a home, so it can’t account for property-level pricing. If the home appraises for less than the purchase price, your loan-to-value ratio rises and the lender’s risk goes up, which usually means a higher rate or a requirement for private mortgage insurance. Fannie Mae also applies loan-level price adjustments that make condominiums and investment properties more expensive to finance than a standard single-family primary residence.3Fannie Mae. Loan-Level Price Adjustment Matrix And if the loan size pushes you above the conforming loan limit, currently $832,750 for a single-unit property in most of the country for 2026, you move into jumbo territory with different pricing and standards.4FHFA. FHFA Announces Conforming Loan Limit Values for 2026
How to Protect Your Rate Before Closing
The gap between pre-approval and closing is where borrowers most often hurt their own rates. Keep your financial picture as close to identical as possible to the day you applied:
- Don’t open new credit accounts. A new card, auto loan, or store financing adds a hard inquiry and raises your total debt.
- Don’t make large purchases on existing credit. Running up a balance increases your utilization ratio, one of the fastest ways to dent your score.
- Don’t change jobs voluntarily. A gap or a shift in how you’re paid gives the lender a reason to pause the file.
- Don’t miss any bill payments. A single 30-day late during this window can drop your score enough to change your terms.
- Don’t make large unexplained deposits. Lenders trace the source of down payment funds, and undocumented cash creates underwriting problems that can delay closing.
Locking In Your Rate
The only way to stop your rate from floating is a formal rate lock. Once you have an accepted offer, you can ask your loan officer to lock, which freezes the rate for a set period. Locks are commonly available for 30, 45, or 60 days, with longer periods available in some cases.5Consumer Financial Protection Bureau. Whats a Lock-In or a Rate Lock on a Mortgage
A lock is not bulletproof. If your application changes after the lock, including your loan amount, credit score, or verified income, the lender can still adjust the rate.5Consumer Financial Protection Bureau. Whats a Lock-In or a Rate Lock on a Mortgage The lock protects you from market movement, not from changes to your own file.
Federal regulations require the Loan Estimate to disclose whether the rate is locked and, if so, when the lock expires down to the applicable time zone.6Consumer Financial Protection Bureau. 12 CFR 1026.37 – Content of Disclosures for Certain Mortgage Transactions (Loan Estimate) If something triggers a revised estimate, the lender must provide an updated Loan Estimate within three business days.7eCFR. 12 CFR 1026.19 – Certain Mortgage and Variable-Rate Transactions Read that document carefully.
When to Lock
Lock too early and you might watch rates fall while yours stays frozen. Lock too late and a spike could cost you thousands over the life of the loan. Most borrowers lock shortly after an offer is accepted, because that’s when the closing timeline becomes concrete enough to fit a 30- to 60-day window. Trying to time the bottom of a dip rarely pays off.
Extended Locks for New Construction
If you’re building, a standard lock won’t cover a timeline that stretches six months or more. Extended locks of 120, 180, or even 360 days exist for this situation. They typically require an upfront fee, often credited toward closing costs if the loan closes on time. If the lock expires before construction finishes, you’ll need to re-lock at the current market rate.
Float-Down Options When Rates Drop
One common worry after locking is watching rates fall below the rate you locked. A float-down provision lets you adjust your locked rate downward if market rates drop by a certain amount before closing. Some lenders include this at no extra cost but require rates to fall by at least a quarter or half a percentage point before you can use it. Others charge an upfront fee, commonly around 0.25% of the loan amount.
If you’re considering a float-down, get the specifics in writing. Ask what minimum rate decrease triggers the option, how the new rate is calculated, and whether a no-fee version is available. The math works best when you’re closing soon and rates look likely to keep dropping.
What Happens If Your Lock Expires
Closing delays happen. Appraisal issues, title problems, and underwriting complications can push your closing past the end of your lock. Extension fees typically run from a fraction of a percent up to about one percent of the loan amount, depending on the lender and how much additional time you need. These fees are usually rolled into closing costs.
The CFPB warns that extending an expired lock can be expensive, so tracking the expiration date is worth treating as a priority.5Consumer Financial Protection Bureau. Whats a Lock-In or a Rate Lock on a Mortgage If closing is drifting and the lock is running out, talk to your loan officer early. Some lenders offer a one-time extension at a reduced cost if you request it before expiration rather than after. Others will re-lock at the current market rate if the lock has already lapsed, which could mean a higher or lower rate depending on where the market has moved.
A rate lock also doesn’t bind you to a particular lender. If your lock expires or you receive a materially better offer elsewhere, you can switch. You’ll restart the application, but if rates have dropped enough, the savings over the life of the loan can be worth it.