A mortgage rate lock, sometimes called a lock-in, is a lender commitment that the stated interest rate will not change before closing if the transaction closes within the lock period and the qualifying application facts remain within the agreement. An unlocked rate can move before closing.
The lock has a start, expiration date and time, product, loan amount, property, and conditions. A change in credit, verified income, appraisal, loan amount, down payment, occupancy, or product can affect pricing even when a borrower believed the rate was locked. The written agreement and updated Loan Estimate control the actual offer.
Closing delays create a separate decision. An extension may cost money, change the pricing, or require another approval. A rental owner should align the lock period with appraisal, title, insurance, entity, lease-document, and lender-underwriting dependencies rather than assuming every closing can meet a short target.
The useful record is not a screenshot of an advertised rate. Keep the lock confirmation, Loan Estimate showing whether the rate is locked, expiration timestamp and timezone, extension terms, changed-circumstance notices, and final Closing Disclosure. That record supports both the financing decision and a later variance review.
Questions to answer before relying on the lock
Ask what exact rate, points, credits, loan amount, and product are covered; which facts can change the price; how long the lock lasts; what an extension costs; and whether a float-down option exists. Record the answers with the expected closing critical path.
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Confirm the expiration date, time, and timezone.
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Identify the person responsible for requesting an extension before expiry.
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Compare the final disclosure with the locked scenario rather than with an advertisement.
This is general educational information, not legal or tax advice. Rules vary by state and locality and change over time — check your local law and confirm specifics with a qualified professional.
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Written and maintained by the Aptoria editorial team
Content updated July 29, 2026. Repository and source review completed July 29, 2026. Aptoria reviews scope, source fit, examples, limitations, links, and publication gates. This record does not claim attorney, CPA, lender, appraiser, or other independent professional sign-off.
Professional review is not claimed. Verify current law, tax treatment, loan terms, valuation inputs, and property-specific facts with the appropriate qualified professional before acting.
Primary and authoritative sources
Related terms
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Loan Estimate
A Loan Estimate is the standardized form that summarizes estimated loan terms, projected payments, closing costs, cash to close, and selected loan features after a mortgage application.
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Closing Disclosure
A Closing Disclosure is the standardized form that states final mortgage terms, projected payments, closing costs, and cash to close for a covered transaction.
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Lender credit
An amount a mortgage lender applies toward closing costs, often in exchange for a higher interest rate than the same lender would offer without the credit.
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Adjustable-rate mortgage (ARM)
A mortgage whose interest rate is fixed for an initial period and then adjusts periodically based on a market index plus a margin.
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