Interest reserves: how lenders size them, and what they really cost.

An interest reserve is part of a commercial real estate loan set aside to pay that loan's own interest while the property cannot, usually during construction, lease-up or a bridge business plan. It is borrowed money: it is sized into the loan amount, and every dollar drawn from it accrues interest at the loan rate, so the reserve partly pays interest on itself. On a floating-rate loan priced over SOFR, 3.66% for the week ending July 31, the reserve is also an assumption about rates for every month it has to cover.

Where things stand, August 4, 2026

• The Fed. On July 29 the Federal Reserve held its target range at 3.50% to 3.75%, where it has been since December. The vote was 9 to 3, and all three dissenters preferred a quarter-point increase. The statement said inflation "remains elevated." The prime rate is 6.75%.
• SOFR. 3.66% for the week ending July 31 (FRED weekly data). Since January the weekly figure has stayed between 3.55% and 3.75%. Most construction and bridge loans we see float over it.
• The 10-year Treasury. 4.75% for the week ending July 31, up 56 basis points from 4.19% in the first week of January. It prices the permanent loan that has to take out a construction or bridge loan.
• Jobs. The June report, released July 2, showed 57,000 jobs added and unemployment at 4.2%, with April and May revised down a combined 74,000. The July report is due August 7.

How an interest reserve works: funded or unfunded

The OCC, which supervises national banks, describes an interest reserve as an account "used by the borrower to cover loan interest during construction and lease-up," typically set up as a line item in the construction budget. There are two ways to hold it, and the difference is real money.

Unfunded, or a holdback. The reserve stays an undrawn part of the loan commitment. Each month the lender advances that month's interest from it and pays itself. You pay interest only on what has been advanced. In our experience, most construction loans work this way.

Funded. The money goes into a lender-controlled interest reserve account at closing, either from loan proceeds or from your own cash. If it comes from the loan, you pay interest on the whole reserve from the first day, while most of it sits in the account waiting to be spent. If it comes from your cash, it is equity sitting idle.

Either way, the reserve never comes from the lender's pocket. Our glossary puts it in one line: it is your money, budgeted honestly.

The math on a $21MM construction loan

Take an illustrative ground-up multifamily project with a $30MM total budget and a construction loan at 70% of cost, $21MM, in line with the up to 70% of cost on our Echo Park construction closing. The rate is SOFR of 3.66% plus an illustrative 3.50% spread, or 7.16%. Construction takes 18 months and lease-up to stabilization takes six, so the lender sizes the reserve for 24 months.

Construction period. About $19.2MM of the loan pays for construction. Drawn evenly, the average balance outstanding over 18 months is about half of that, $9.6MM. At 7.16%, $9.6MM costs about $687,000 a year, and over a year and a half about $1.03MM.

Lease-up. The full $19.2MM is now outstanding for six months. That is $19.2MM times 7.16%, divided by two, or about $687,000.

Interest on interest. Those two pieces total about $1.72MM. But each month's interest is itself a loan advance, and it accrues at 7.16% until the loan is repaid. Run month by month, that adds about $84,000. The reserve comes to about $1.80MM, or 8.6% of the loan. Monthly interest starts near $3,200, reaches about $117,000 when construction finishes, and ends near $125,000.

So of a $21MM loan, only about $19.2MM builds the building. The calculation is circular, since a larger reserve means a larger loan and more interest, and lenders solve it in a spreadsheet. The owner's job is to know the answer before the term sheet arrives.

What it really costs. Beyond the interest you would owe anyway, three costs are easy to miss. The interest on interest, about $84,000 here. Fees: at one origination point on the full commitment, about $18,000 of fees fall on the reserve. And equity: because the reserve is a line in the budget and the lender funds 70% of the budget, putting $1.8MM of interest into the project raises your equity requirement by about $540,000.

The bridge version. A $10MM bridge loan is fully funded on day one, so there is no draw curve. At an illustrative SOFR plus 4.50%, or 8.16%, twelve months of interest is $816,000 before compounding. As a holdback drawn monthly, the reserve comes to about $847,000. As a funded reserve advanced at closing, it has to cover interest on itself for the full year, about $888,500. Same loan, same rate, about $41,000 apart.

Why lenders require them, and how they size the months

A construction site, a vacant building in lease-up and a parcel of land produce little or no income. A lender cannot underwrite monthly interest from cash flow that does not exist yet, so it reserves for it. Bridge lenders reserve when the business plan cuts income, during a renovation or a re-tenanting.

The OCC's guidance to bank examiners is to size the reserve to pay interest "through the project's anticipated completion" and lease-up, and to test the assumptions behind it, "including potential changes in interest rates." In practice that means construction months plus lease-up months to stabilization for a construction loan, and the months to stabilization or the initial maturity for a bridge loan. In our experience, many lenders run the numbers at a stressed rate or at the strike of the required rate cap rather than at today's SOFR.

Land is the exception banks avoid: the same OCC guidance calls reserves on speculative raw land generally inappropriate. In our experience, private and debt fund land lenders often hold back interest anyway, because dirt pays nothing. On a $1MM land loan at 11.00%, the rate on a Morgan Hill land bridge we arranged, one month of interest is about $9,200, and a year would be $110,000, or 11% of the loan. Our guide to land development financing in Los Angeles covers how that carry fits the stages from unentitled to vertical.

When the reserve runs out, and what a 50 bps move in SOFR does

Hold the $21MM example's budget fixed and raise SOFR by 50 basis points for the life of the loan, to a 7.66% rate. The 24 months of interest now cost about $1.93MM. The reserve is short about $132,000, roughly one month of interest at the end. Delay is worse: each extra month at the full balance costs about $125,000 at the original rate. A lease-up that runs three months long, plus the half-point move, would leave the reserve short about $540,000.

When that happens the loan is out of balance. Construction loan agreements typically carry an in-balance clause that requires the borrower to deposit the shortfall or put in more equity; sample clauses give ten business days after notice. The OCC says banks generally look to the borrower or guarantor for more cash, and it tells examiners that the decision to "repack the interest reserve with debt is a red flag." Do not plan on the lender refilling it.

Extensions bring their own tests. Typical conditions in sample extension clauses include no default, a fee of 0.20% to 0.25% of the balance, a coverage or debt yield test, and a rate cap in place for the extended term. A bridge loan whose reserve is spent and whose property has not hit the test is a cash call, not an extension.

Interest reserves vs debt service and replacement reserves

An interest reserve pays interest because there is no income, and it is meant to be spent down to zero. A debt service reserve is a cushion on an income-producing loan: a set number of months of payments held in cash, not meant to be touched, and usually released once the property passes a coverage test. Lenders use it when coverage is thin or a major lease is at risk. A replacement reserve is a monthly deposit for roofs, mechanical systems and other capital items, common on permanent loans. Only the first one pays your interest.

What owners should negotiate

• Ask for a holdback, not a funded reserve. You pay interest only on what is drawn. On the $10MM bridge above, that is about $41,000.
• Build your own reserve model first. Size it to your schedule, then stress it 50 basis points higher and three months longer. Know the shortfall before the lender does.
• Get budget reallocation rights. Unused contingency and cost savings should be able to move into the interest line without a new credit approval.
• Negotiate the cure. If the loan goes out of balance, ask for a cure period you can actually meet and the right to cure with equity on a schedule.
• Settle lease-up income now. Lease-up income ordinarily pays interest before the reserve is touched. Agree how the unused reserve is treated at stabilization or extension.
• Compare quotes on total carry, not spread. Two term sheets with the same spread can carry different reserves, fees and extension tests. Put them side by side on total interest carry, points and extension costs before you choose.

Quick answers

What is an interest reserve? Money set aside inside a construction, bridge or land loan to pay that loan's interest while the property earns too little to pay it. It is usually part of the loan amount, and you pay interest on it once it is drawn.

What is an interest reserve account? A lender-controlled account holding a funded reserve, deposited at closing from loan proceeds or the borrower's cash. The lender pays the monthly interest from it.

How is an interest reserve calculated? Average balance outstanding, times the rate, times the months to be covered, plus interest on the interest already drawn. On our $21MM example at 7.16% over 24 months, about $1.80MM.

What happens when an interest reserve runs out? The loan goes out of balance, and the borrower usually has to deposit cash or add equity within a short notice period. Do not count on the lender refilling it with new debt.

If you are pricing a construction, bridge or land loan and want the reserve modeled before you sign, send us the deal. We will tell you within two business days what the market will lend and what the interest carry really looks like.

Sources. Fed decision and statement: Federal Reserve, July 29, 2026. Prime rate: FedPrimeRate.com, July 29, 2026. SOFR and 10-year Treasury, weekly: FRED SOFR and FRED DGS10, week ending July 31, 2026. Jobs: BLS Employment Situation for June 2026, July 2, 2026; BLS release schedule. Interest reserve guidance: OCC Comptroller's Handbook, Commercial Real Estate Lending, Version 2.0, March 2022. Average balance method: PropertyMetrics, updated January 7, 2023; A.CRE glossary, updated July 3, 2025. Loan balancing and extension clauses: Law Insider sample clauses, loan balancing and first extension option (undated sample clauses). The loan examples are illustrative; the 70% loan-to-cost (up to 70% at closing) and the 11.00% land rate are from closings arranged by Piccard Financial.

Rates and terms referenced are drawn from public market data, transactions arranged by Piccard Financial and recent lender quotes, reflect conditions on the dates shown, and change with the market. Nothing here is an offer or a commitment to lend. Piccard Financial is a capital markets advisory firm, not a lender.