What Is a Rate Lock?
A rate lock is a contractual commitment from a mortgage lender to hold a specific interest rate for a defined period, typically 30 to 60 days, while the borrower's loan application is processed and the transaction moves to closing. During the lock period, the borrower is protected from market rate increases—the agreed rate applies at closing regardless of where interest rates move.
Rate locks are a standard tool in residential mortgage transactions because the time between loan application and closing—during which the mortgage rate is determined and applied—is long enough for rates to move materially. Without a rate lock, a borrower who applied at 6.75% could face 7.25% at closing if rates rose during processing.
How Rate Locks Work
When a borrower and lender agree on a rate lock:
- The lender specifies the locked rate, the lock period (in days), and any lock-specific terms or fees.
- The lock is documented in writing, typically in the Loan Estimate or a separate lock confirmation.
- As long as the loan closes within the lock period, the borrower receives the locked rate regardless of market movements.
- If rates fall during the lock period, the borrower does not automatically receive the lower rate (absent a float-down provision).
- If the lock expires before closing, the borrower must re-lock, pay an extension fee, or close at the then-current market rate.
Rate locks typically apply to both the interest rate and the points structure agreed upon at the time of locking. A lock on a specific rate with zero points at locking remains at zero points; the locked rate cannot be repriced.
Lock Period Lengths and Cost
Lock periods are priced by duration:
- 15–30 days: Shortest available; lowest cost. Used for transactions close to closing or with rapid processing timelines. Not practical for most purchases.
- 45 days: Standard for most purchase transactions in normal markets. Allows time for typical underwriting and closing timelines.
- 60 days: Used when additional processing time is anticipated—complex income documentation, multiple property types, or anticipated delays.
- 90+ days: Required for new construction, delayed closings, or refinances with extended timelines. Significantly higher cost.
The pricing difference between lock periods reflects the lender's exposure to rate changes. A 60-day lock requires the lender to hold pricing risk twice as long as a 30-day lock. The additional cost is typically expressed as a pricing adjustment to the rate (e.g., 0.125% higher rate for a 60-day lock vs. 30-day) or as an upfront lock fee.
Floating vs. Locking
Until the borrower officially locks, the loan is said to be "floating"—the rate will be whatever the market rate is at the time of locking. Floating is a speculative position: the borrower is betting that rates will fall before they lock, saving money relative to locking now.
Floating carries risk. Rates can and do move significantly over days and weeks in response to economic data releases, Federal Reserve communications, inflation reports, and geopolitical events. A borrower who floats hoping for a 0.125% rate improvement may find rates have moved 0.375% against them.
For most borrowers—particularly first-time buyers or those without sophisticated fixed-income market knowledge—locking promptly after application eliminates rate risk and allows focus on the transaction itself. This is especially relevant when comparing a fixed-rate mortgage against an adjustable-rate mortgage, where the locked rate has different long-term implications.
Float-Down Options
A float-down provision is an add-on to a rate lock that allows the borrower to receive a lower rate if rates fall by a specified amount during the lock period. Float-down options address one of the primary criticisms of standard rate locks: they protect against rate increases but provide no benefit if rates decline.
Float-down terms vary significantly by lender:
- Trigger: Rates must fall by at least a specified amount (often 0.25–0.50%) before the float-down activates.
- Cost: An upfront fee (typically 0.125–0.5% of the loan amount) or an incrementally higher locked rate.
- Timing: Float-down rights are often exercisable only once, within a specific window during the lock period.
- New rate: The borrower typically receives the then-current market rate, not the full decline—there may be a partial benefit (e.g., 50% of the rate drop is passed through).
Float-down options are most useful in volatile rate environments where the borrower has strong reason to expect rates to fall but cannot wait to apply.
Extended Locks for New Construction
New construction purchases present a particular challenge for rate locks. Closing dates are often uncertain—construction delays, material shortages, permitting issues, and weather can push closings months beyond initial estimates. A 60-day lock is usually insufficient for a new construction purchase, and lenders may not offer standard locks for transactions with highly uncertain close dates.
Solutions include:
- Extended locks (90–180+ days): Available at a significant premium over standard lock periods.
- Float-down with extended period: Some lenders specialize in new construction and offer extended locks with float-down rights.
- Commitment fee structure: The borrower pays a commitment fee upfront for an extended lock, some of which is credited back at closing.
Builders sometimes offer rate lock programs through preferred lenders as an incentive to buyers, which may provide more competitive extended-lock pricing than borrowers could obtain independently.
Rate Lock Expiration and Extensions
If the lock expires before closing, the borrower has options depending on market conditions and lender policy:
- Lock extension: The lender extends the lock for an additional period at a cost. Extension fees typically run 0.125–0.375% per extension period.
- Re-lock: Surrender the original lock and re-lock at current market rates. If rates have risen, this results in a higher rate than originally locked; if rates have fallen, this could produce a lower rate.
- Float: If closing is genuinely imminent (within days), some borrowers choose to float briefly rather than pay an extension fee.
Most lenders absorb the cost of extensions caused by their own processing delays, while borrowers bear the cost of extensions caused by borrower-related delays (document deficiencies, appraisal issues, etc.).
Common Misconceptions
A rate lock is the same as loan approval. A rate lock preserves a rate; it does not guarantee loan approval. Underwriting continues after locking, and a loan can be denied or require conditions even after the rate is locked.
The locked rate is guaranteed regardless of changes in the loan. Significant changes—increased loan amount, different property, or change in occupancy type—may void the lock or trigger a re-pricing. Minor adjustments within program parameters typically do not affect it.
Locking always costs extra. Standard 30–45 day locks typically carry no separate fee; the lock period is priced into the rate itself. Fees are most commonly associated with longer locks or float-down options.
AI Tools in Rate Lock Decisions
AI tools supporting mortgage decisions can help borrowers track rate environments, model the cost of different lock periods, and evaluate float-down options. Approval AI and Securelend Agents provide financing decision support. Moveorinvest and Homescore assist with broader homeownership financial modeling.
For buyer financing decision context, see AI tools for first-time home buyers financing. Compare platforms at ChatRealtor vs Whiterook. The 2026 AI tools guide covers proptech across the homebuying process.