The quick read: An interest reserve is money set aside inside a construction loan to pay that loan's own interest while the building cannot. The lender establishes it as part of the initial loan commitment, advances each month's interest from it and adds that interest to your balance, so you write no interest check during the build. Once the project's cash flow covers the interest, draws on the reserve should stop. If delays or higher rates drain it first, you or your guarantor fund the gap.
What is an interest reserve on a construction loan?
An interest reserve is an account the lender sets up so the borrower can pay construction loan interest during the build and lease-up, usually funded as a budget line inside the loan and sometimes with the borrower's own cash in a separate escrow. It exists because an unfinished building earns no rent.
That definition comes from the Office of the Comptroller of the Currency's Commercial Real Estate Lending handbook (Version 2.0, March 2022), which tells bank examiners how to review these loans. The handbook treats interest as a construction cost like any other: it says interest expense should be properly estimated and reserved for, and that an appropriate reserve provides sufficient funds to pay interest through the project's anticipated completion and lease-up, sale or occupancy.
The interagency policy statement on CRE loan accommodations and workouts, issued June 30, 2023 by the Federal Reserve, FDIC, NCUA and OCC, describes the same structure from the lender's books. At origination, the lender establishes the interest reserve as a portion of the initial loan commitment. During construction it recognizes interest income from the reserve and capitalizes the interest into the loan balance. After completion, sale proceeds or a permanent loan repay principal, including the capitalized interest, or the construction loan converts to an amortizing loan.
Reserve location, OCC handbook: a budget line in the construction loan, or a borrower-funded escrow required as a condition of the loan
Reserve period, OCC handbook: through anticipated completion and lease-up, sale or occupancy
Accounting, interagency statement (June 30, 2023): interest capitalized into the loan balance during construction
How does the reserve pay the interest each month?
Each month the lender calculates interest on the balance actually advanced, pays that interest to itself from the reserve line and adds the same amount to your loan balance. The reserve shrinks, the loan grows, and next month's interest is charged on a slightly larger number. You never send a payment.
That capitalization has three consequences for an investor. First, you pay interest on interest, because last month's capitalized interest is now principal. In the example below, compounding adds about $35,700 over 24 months compared with paying the same interest from a separate cash account.
Second, the loan stays current whether or not the project is on track. The interagency statement warns that if a development stalls and the lender fails to evaluate the loan's collectability, interest can keep being recognized from the reserve and capitalized even though the project is not generating enough cash flow to repay the loan; the loan is then contractually current because the reserve funds the payments, while repayment of principal may be in jeopardy. A current loan is not proof that your schedule is holding.
Third, the bill arrives at the exit. Every dollar of capitalized interest is repaid from the sale or the takeout loan, so a larger reserve means less net cash at the finish line.
How is an interest reserve sized?
An interest reserve is sized by projecting the loan balance month by month from the draw schedule, applying the contract rate to each month's balance and carrying the total through completion and lease-up, sale or occupancy, with room built in for higher rates and a slower schedule than the base plan.
The OCC handbook lists the inputs it expects a bank to test: potential changes in interest rates, the timing of expected disbursements and paydowns, and the time needed to complete and sell or lease up the project. The draw timing matters most, because money advanced in month 17 accrues interest for far fewer months than money advanced in month 2.
Illustrative example (our arithmetic, not a lender quote or current pricing): a project costs $15.0 million before financing interest. The sponsor's $5.25 million of equity funds at closing, then the loan advances $9.75 million of construction costs across an 18-month build on an S-shaped draw curve, at an assumed fixed 8.00%. Lease-up takes six months, with property cash flow covering 0%, 20%, 40%, 60%, 80% and then 100% of each month's interest. Interest is capitalized.
Construction-period interest (our arithmetic): about $639,000
Lease-up interest (our arithmetic): about $209,000
Total interest reserve, base case (our arithmetic): about $848,000
Same reserve with a rate 1 percentage point higher (our arithmetic): about $959,000
Same reserve with a 21-month build (our arithmetic): about $956,000
Both changes together (our arithmetic): about $1,082,000, about 28% above the base case
Two shortcuts go wrong in opposite directions. Charging 8.00% on the full $9.75 million for all 24 months gives $1.56 million, nearly double the modeled need, which spends loan proceeds on interest that never accrues. Stopping the model at the end of construction leaves about $209,000 of lease-up interest unfunded, which is the shortfall that surfaces just as the building opens.
If the loan floats, the reserve moves with the benchmark. SOFR was 3.94% on October 28, 2026 and the bank prime loan rate was 7.00% on October 27, 2026, according to FRED's SOFR and prime rate series. On October 28, 2026 the FOMC held the target range for the federal funds rate at 3-3/4 to 4 percent, and two voting members preferred a 1/4 point increase. A reserve sized at today's benchmark with no cushion has no room for a higher one. The stress-test guide walks through the rate, delay and combined cases in detail.
Should the reserve sit inside the loan or in a borrower escrow?
Putting the reserve inside the loan saves cash at closing but raises the loan amount and loan-to-cost, while a borrower-funded escrow keeps the loan smaller and avoids interest on interest at the price of more equity on day one. The right choice depends on your liquidity and the lender's loan-to-cost limit.
The OCC handbook adds a point that matters for the escrow route: when the bank will not fund the interest, examiners consider whether there is enough equity for the bank to fund it if necessary while keeping the loan within appropriate loan-to-cost and loan-to-value ratios, even if the borrower intends to pay interest from its own funds. A lender can size an escrowed deal as if it might end up carrying the interest anyway.
Table: Interest reserve inside the loan versus borrower escrow (illustrative, our arithmetic on the example above)
| Line | Reserve inside the loan | Borrower-funded escrow |
|---|---|---|
| Line Who funds the reserve | Reserve inside the loan The lender, as a budget line in the commitment | Borrower-funded escrow The borrower, in cash at closing |
| Line Who releases the money | Reserve inside the loan The lender, as a monthly advance | Borrower-funded escrow The lender, from the escrow it requires |
| Line Interest funded over 24 months | Reserve inside the loan About $848,000 | Borrower-funded escrow About $812,500 |
| Line Loan amount | Reserve inside the loan About $10.6 million | Borrower-funded escrow $9.75 million |
| Line Total project cost | Reserve inside the loan About $15.85 million | Borrower-funded escrow About $15.81 million |
| Line Loan-to-cost | Reserve inside the loan 66.9% | Borrower-funded escrow 61.7% |
| Line Sponsor cash at closing | Reserve inside the loan $5.25 million | Borrower-funded escrow About $6.06 million |
| Line Interest charged on capitalized interest | Reserve inside the loan Yes | Borrower-funded escrow No |
| Line If the reserve runs short | Reserve inside the loan Sponsor adds cash, or the lender may repack with new debt | Borrower-funded escrow Sponsor adds cash |
The in-loan structure replaces about $812,500 of sponsor equity with about $848,000 of debt and lifts loan-to-cost by about 5.2 points. If the lender's loan-to-cost ceiling sits below 66.9% on this project, the reserve has to come partly from equity anyway. Run your own budget through the loan-to-cost calculator with the reserve both in and out of the loan before you compare term sheets.
When do draws on the interest reserve stop?
Draws on an interest reserve should stop once the project's own cash flow covers the interest, because the OCC handbook says lease-up income is ordinarily applied to interest before the reserve and that no further reserve draws should be permitted once that income is sufficient.
The handbook's stated reason is to prevent the diversion of income that should be used to support the project. In the example, reserve draws fall from about $69,000 a month at the start of lease-up to zero in month 24, when rent covers the full interest bill. The reserve fills the gap between rent and interest; it does not replace rent the building is already earning.
The same logic explains where reserves do not belong. The OCC handbook says using interest reserves on loans that should be generating cash flow, such as stabilized properties, or on speculative purchases of raw land is generally not appropriate. If you are buying a leased building, expect the lender to size the loan on the property's income instead.
Reserve money left over is not free cash either. The handbook lists borrower requests to reallocate significant funds to other budget lines among its warning indicators, so moving unused reserve into hard costs is a request the lender will scrutinize. Ask at term sheet what happens to an undrawn balance.
What happens if the interest reserve runs short?
If the reserve runs short, the lender generally requires the borrower or guarantor to put in cash to cover interest or replenish the reserve. A lender that instead adds new debt to refill it, called a repack, is treated by bank examiners as a red flag for possible credit deterioration.
The OCC handbook says depletion often follows construction delays or a change in market conditions. To support a repack, it calls for a new appraisal or evaluation and a fresh look at the project's feasibility in the current market, and it lists repacked interest reserves among the warning signs examiners watch. The interagency statement includes a worked case: a lender committed an additional $48,000 interest reserve and extended a $1.2 million loan for 12 months; the examiner disagreed with the lender's pass grade, $18,000 of capitalized interest was reversed and the loan was placed on nonaccrual.
For a sponsor, that means a refill request triggers a re-underwrite, not a formality. Track the remaining reserve against the schedule at every draw, and decide early whether the answer is your own cash, a budget change or new financing. The guide on what to do before an interest reserve runs out covers those moves.
If the construction loan matures in the next 6 to 12 months and lease-up is behind plan, the reserve and the maturity become one problem. Line up the extension, or the bridge or permanent takeout, while reserve remains to carry interest; once the reserve is gone, every month of negotiation is paid from your own cash.
How do you get a construction loan placed with the right interest reserve?
YieldStack publishes this guide, and our recommendation is to place a construction loan through a commercial mortgage brokerage that sizes the reserve from your draw schedule and puts each lender's reserve treatment, rate and loan-to-cost side by side before you choose.
Option 1, the brokerage route (our recommendation). YieldStack is an AI-native commercial mortgage brokerage that arranges financing for commercial real estate investors. Software matches the deal against 20,000+ loan programs and compares the options; human brokers structure the deal, negotiate on the borrower's side and carry it toward closing. On a construction loan, that structuring includes the reserve: in the commitment or in escrow, the rate cushion, and whether the lease-up months are funded. The median first offer arrives in under an hour, from an institutional lender. It costs Zero upfront to submit a deal and review offers; YieldStack's broker fee is 0.50–1.00% of the loan amount and is paid only at closing. Every credit decision is made by the lender; YieldStack arranges the introductions and negotiates on the borrower's side, and no loan, rate, or closing is guaranteed.
Option 2, your relationship bank. A bank that knows your completions can move quickly on a familiar sponsor, but you see one lender's reserve sizing and one loan-to-cost limit.
Option 3, fund the interest from your own cash. A borrower escrow keeps the loan smaller and the interest uncompounded, at the cost of more equity at closing and a lender that may still size the deal as if it could carry the interest.
The package that gets comparable answers on reserve sizing:
- Hard and soft cost budget with the interest reserve as its own line
- Monthly draw schedule tied to the construction timeline
- Lease-up or sales schedule with the rent or price assumptions behind it
- The rate and delay cases you used to size the reserve
- Sponsor liquidity available to replenish the reserve if it runs short
When the budget and draw schedule are ready, submit your construction deal for a reserve and terms comparison. Product terms are on the construction loans page.
The bottom line
An interest reserve is the construction loan paying its own interest until the building can. The lender sets it inside the commitment, or holds your cash in escrow, advances interest monthly and capitalizes it. Size it from the draw schedule through lease-up, test higher rates and a longer build, stop draws once rent covers interest, and decide now who refills it if it runs short.