Mortgage Banking — Interest Rate Lock Commitment (IRLC) as Derivative at Fair Value
Recording an interest rate lock commitment issued to a mortgage borrower as a derivative asset or liability — the lock obligates the lender to fund the mortgage at the agreed rate, creating market risk exposure.
| Account Name | Type | Debit ($) | Credit ($) |
|---|---|---|---|
| IRLC Derivative Asset (Fair Value of Rate Lock — If Rates Rise) | Asset (+) | 8,500,000.00 | - |
| Gain on IRLC (Fair Value Change — P&L or OCI Depending on Hedge) | Income (+) | - | 8,500,000.00 |
💡 Accountant's Note
When a mortgage lender locks a borrower's interest rate for 30-60-90 days, the lender has created an IRLC — a commitment to originate a mortgage at a specified rate regardless of where market rates move. Under ASC 815: the IRLC is a derivative (it has a notional amount = loan amount, underlying = interest rate, no initial net investment, and net settlement ability through the forward MBS market). The IRLC is marked to market with changes through the income statement. If interest rates RISE after the lock is issued: the fixed-rate loan becomes more valuable than market (the borrower got a lower rate than current market) → IRLC has a POSITIVE fair value to the lender (they have a below-market-rate loan to sell into the secondary market at a premium). IRLC fair value = loan value at locked rate − loan value at current market rate, adjusted by the pull-through rate (probability that the application closes, typically 70–85%).
Practitioner & Systems Framework
💻 ERP Architecture
The mortgage pipeline (all IRLCs outstanding) is managed by the secondary markets desk. The key variable: PULL-THROUGH RATE — what percentage of locked applications will actually close? Applications where the borrower is under contract (more certain to close) have higher pull-through than speculative locks. The pipeline fair value = sum of (loan amount × (locked rate value − market rate value) × pull-through %) across all locks. Most mortgage bankers use forward mortgage-backed securities (TBA — To-Be-Announced) as the hedge instrument — a short TBA position offsets the IRLC's price risk.
⚠️ Audit Flags
IRLC derivative valuation and the pull-through rate are the most judgmental aspects of mortgage banking accounting. Auditors test: (1) The market rate used for fair value calculation — is it the current secondary market rate for comparable loans? (2) The pull-through rate — is it based on historical close rates for similar loan applications? (3) The TBA hedge — is it effective in offsetting the IRLC's fair value changes? Pull-through rates that are systematically overstated inflate IRLC fair values (overstating assets) in a refinancing boom.
📄 Required Documentation
IRLC pipeline report (loan amount, rate, lock expiry, pull-through, FV), market rate source (pricing engine — Optimal Blue, Black Knight), pull-through rate model and historical validation, TBA hedge position details and effectiveness assessment, daily mark-to-market of pipeline, and secondary market rate source documentation.
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