SOFR Isn't Your Index: How Lookback, Lockout, and Payment Delay Conventions Change Effective Interest Accrual and Default Timing

The Index Isn't What You Think It Is

When a loan agreement says "SOFR plus 275 basis points," you're reading the punchline, not the joke. The real structure lives in the definitions section: how that SOFR rate is observed, when it's locked, how many days it's delayed, and whether it applies to the entire accrual period or fragments of it. These conventions don't just affect your monthly payment by rounding errors. They reshape your effective all-in cost of capital, alter the timing of cash outflows, and change the precise moment a default can be declared.

Lenders know this. Borrowers often don't. That gap is where friction lives, and where unexpected leverage emerges in workouts.

Lookback Conventions: When the Rate You Pay Isn't Today's Rate

Under a "lookback" convention, the rate isn't set on the day interest accrues. Instead, it's observed on a date earlier in the period, often 2 or 5 business days before the interest period begins or ends. This delay has three material consequences:

For borrowers, a lookback creates a rate-lock effect. If SOFR is rising, you benefit because your payment is based on last week's lower rate. If SOFR is falling, you pay more than you'd prefer. The implication: your budgeted interest expense can drift meaningfully from forward curves if you're not modeling the lookback lag explicitly.

For lenders, a lookback extends the duration of their rate risk. They've funded you at today's cost, but they don't know what rate they're receiving until several days into the period. This is priced into spreads, and it shows up as basis risk in hedging. A lender managing a matched-book portfolio will charge a wider spread to offset the uncertainty of not knowing their own cost of funds until after they've deployed them.

In practical terms: if you're modeling all-in carry at SOFR plus 275, but your loan uses a 5-day lookback and rates are volatile, your actual rate could easily be 10 to 15 basis points higher or lower than your term sheet assumption. That compounds over a 5-year hold.

Lockout Periods: When You Can't Refinance, But Interest Still Accrues

Lockout periods prevent prepayment or refinancing for a defined window, typically the first 2 to 3 years of a loan. But lockout language often contains a hidden mechanics clause: during the lockout, does SOFR still reset every month, or is it fixed for the entire lockout period?

If SOFR resets monthly during lockout, you're paying a floating rate you can't escape. Your interest expense moves with the market, but you can't refinance or hedge. If rates spike 200 basis points in year two, you're stuck paying the higher rate until either the lockout expires or you breach a covenant and get forced out.

If SOFR is fixed for the lockout period, you have certainty, but at a price: lenders typically charge 25 to 50 basis points more to lock in their spread over a multi-year period. The trade-off is rate certainty versus cost.

What this means: a "locked-out" borrower in a rising-rate environment is actually in a worse position than a borrower with a shorter lockout and a wider spread. The lockout convention transforms an optional refinancing right into a structural liability. Lenders know this and price it accordingly. Borrowers often sign the term sheet without modeling the rate path that would make the lockout binding.

Payment Delay Conventions: The Accrual-to-Cash Gap That Changes Default Timing

Interest accrues daily but is paid in arrears, typically 5 to 10 business days after the end of the interest period. This isn't a rounding detail. It's a covenant mechanics issue.

Most loan agreements define a payment default as a failure to pay accrued interest on the stated payment date. But if your loan requires you to deposit funds 5 business days before the payment date (for example, into a lockbox or servicer account), the actual default trigger occurs at that deposit deadline, not the payment date itself. If you're short by one day, you're in technical default even though the payment isn't due for another week.

This matters in two scenarios:

First, in a tightly managed cash-flow situation, the deposit requirement can force you into default before the formal payment date arrives. A borrower might have sufficient cash on day 20 of a 25-day month, but the deposit deadline is day 15. That's a structural default risk that doesn't show up in your debt service coverage ratio.

Second, in a workout or forbearance negotiation, the payment delay convention determines when the clock starts on cure periods. If your loan agreement gives you 3 business days to cure a missed payment, those 3 days begin either from the accrual date, the payment date, or the deposit deadline, depending on how the language is drafted. A 3-day cure window can become a 1-day window if the deposit deadline is buried in the definitions.

For lenders, payment delay conventions are a liquidity management tool. They ensure that funds clear and are deployed before the next accrual period begins. For borrowers, they're a hidden leverage multiplier. You're not just borrowing at SOFR plus 275; you're also structuring your cash management around a payment schedule that starts before the month ends.

The Composite Effect: How These Mechanics Stack

A typical transitional loan might combine a 5-day lookback, a 2-year monthly reset during lockout, and a 5-business-day payment delay. What does this actually mean?

Your accrued interest on day 30 of the month is based on SOFR observed on day 25. You owe payment on day 35, but you must deposit funds on day 30. If SOFR spiked on day 26, you don't feel it in this month's payment, but you will next month, because the lookback window has shifted. You're always paying last week's rate, which creates a lag between market conditions and your cash outflow. Lenders hedge this. Borrowers budget for it inconsistently.

The implication: when you model all-in carry, you can't just use the spot SOFR rate. You have to project the forward curve, apply the lookback lag, account for the lockout mechanics, and discount the payment delay. Most underwriting models do this poorly. The result is that actual interest expense often exceeds the budgeted amount by 20 to 50 basis points, which cascades into debt service coverage misses and equity burn.

What I'm watching next:

• Whether lenders start standardizing payment delay language as rates remain volatile, or whether they preserve the asymmetry that allows them to call technical defaults without actually missing cash flow.
• How borrower-side systems are evolving to model lookback and lockout mechanics into monthly cash-flow forecasting, versus relying on static term sheet assumptions.
• Whether the next round of transitional lending includes more explicit SOFR floor language tied to the lookback convention, effectively creating a hybrid fixed-floating structure that borrowers don't fully recognize.