Net operating income sits underneath both of the ratios covered in this course's first two content modules — it is the numerator in DSCR and, as module 04 covers, the number capitalization rates are built around. Getting NOI right is arguably the single most consequential calculation on a commercial file, because every other major figure downstream depends on it.
In its simplest form, NOI is calculated as: gross potential income, minus a vacancy and credit-loss allowance, minus operating expenses, stopping before debt service, capital expenditures, depreciation or income tax. That last point is worth underlining — NOI is deliberately calculated before the mortgage payment, because the whole purpose of the number is to measure the property's income independent of how it happens to be financed, so that DSCR can then compare that income to a specific loan's payments.
Gross potential income is what the property would earn if every unit or space were leased at market rent with no vacancy or non-payment at all — essentially a best-case ceiling. From there, a vacancy and credit-loss allowance is deducted, even on a property that happens to be fully occupied today, because lenders are underwriting to a normalized, sustainable level of income rather than a single point-in-time snapshot that might reflect unusually good (or bad) luck. The specific allowance applied varies by property type and local market — a well-located multi-unit residential building in a tight rental market typically supports a lower allowance than an older retail plaza with tenant turnover risk — and is set by the lender's or appraiser's judgment rather than a fixed national percentage.
Legitimate operating expenses deducted to reach NOI include property taxes, insurance, utilities where paid by the owner, property management fees, ordinary repairs and maintenance, and similar recurring costs of operating the building. What is deliberately excluded from this calculation is just as important: mortgage principal and interest, capital expenditures (a new roof, a major system replacement — these are capital improvements, not operating costs), depreciation, and the owner's income tax. A lender adding debt service or capital costs into the NOI calculation would be double-counting against the DSCR test, since debt service is the figure NOI is being compared against, not a cost buried inside it.
Small commercial and multi-unit files, in particular, often arrive with financial statements shaped by the current owner's personal tax planning rather than a clean picture of the property's actual operating economics — a familiar echo of the add-back conversation in Course 03 on self-employed borrowers, applied here to a property instead of a person. An owner might run personal expenses through the property's books, pay themselves an above-market management fee, or defer maintenance that a new owner would need to catch up on. A careful underwriter or appraiser normalizes these: adding back genuinely one-time or personal items, but also, just as importantly, adjusting down for expenses the current owner understated, such as deferred maintenance that a market-rate operator would actually be spending on repairs.
This cuts both ways, and a broker presenting a file should expect a lender to ask hard, specific questions about any NOI figure that looks unusually strong relative to the property's age, condition and local market — an inflated NOI produces an inflated cap-rate valuation and an inflated DSCR, and a competent underwriter is trained to be skeptical of numbers that look too good without documentation behind them.
A borrower's financial statements show mortgage interest deducted as an operating expense before arriving at net operating income. Is this correct?
NOI is defined specifically to exclude debt service, capital expenditures and income tax, precisely because the whole point of the figure is to measure the property's income independent of financing, so it can then be tested against a specific loan's payments through the DSCR ratio. Deducting mortgage interest before calculating NOI would understate the number and effectively hide the very cost DSCR is meant to test against — a structural error, not a judgment call, and one that has nothing to do with insured status or unit count.
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