Glossary · Income and the rent roll

Net operating income

Also called NOI.

Net operating income is a property's effective gross income less all operating expenses, before debt service, income taxes, depreciation and capital expenditure. It is the figure a cap rate is applied to, the numerator of debt yield and DSCR, and the number a purchase price is ultimately negotiated against.

Updated August 6, 2026 · All terms

How it works

NOI is deliberately capital-structure blind. Two buyers with different loans, different tax positions and different depreciation schedules should compute the same NOI on the same building, which is what makes it comparable across a market and usable as a valuation input. The moment something below the line creeps above it, that comparability is gone.

The recurring fight is over what counts as operating. Real estate taxes, insurance, utilities, repairs and maintenance, contract services, payroll, management fee, general and administrative and marketing are operating expenses and always belong above the line. Debt service, income tax, depreciation, amortisation, partnership fees, capital improvements and leasing costs are below it. The genuinely contested items are replacement reserves, tenant improvements and leasing commissions: appraisers and lenders normally deduct reserves above the line, and many seller pro formas do not.

Because value is NOI divided by a small number, an error in NOI is amplified enormously. At a 5.4 percent cap rate, one dollar of overstated NOI is $18.52 of overstated value. A $55,000 reserve line that was quietly left out moves the implied value by more than a million dollars.

Formula

NOI = effective gross income - operating expenses
  • Above the line: taxes, insurance, utilities, repairs and maintenance, contract services, payroll, management fee, general and administrative, marketing
  • Below the line: debt service, income taxes, depreciation, capital expenditure, tenant improvements, leasing commissions, partnership fees
  • Replacement reserves are treated inconsistently across the market and must be checked on every statement

Worked example

Why the reserve line matters more than it looks

Same property, same expenses, one line moved. Cap rate held at 5.40 percent.

Effective gross income$4,727,800
Operating expenses excluding reserves($1,708,000)
NOI as the seller presents it$3,019,800
Replacement reserves at $250 a unit($55,000)
NOI with reserves above the line$2,964,800
Value difference at a 5.40% cap$1,018,519

A $55,000 annual line item is worth just over a million dollars of purchase price. Whether reserves sit above or below the line is not a presentation preference, it is a price negotiation.

Conventions worth knowing

  • Lenders almost always underwrite reserves above the line, so a loan sized on the seller's NOI will come back smaller than expected.
  • Trailing NOI, normalised NOI and pro forma NOI are three different numbers. Every conversation about a deal should specify which one is being quoted.

The common mistake

Buying on a pro forma NOI and financing on a trailing one

The purchase price gets negotiated against a forward NOI that assumes rents pushed, expenses fixed and vacancy tightened. The lender sizes the loan against trailing performance with normalised taxes and insurance and reserves deducted. The two numbers can differ by 15 percent or more, and the gap shows up as a funding shortfall at closing rather than as a modelling error, because nothing in the model was arithmetically wrong. Run both and size the equity against the lender's version.

Related terms

Every figure, traced to its source

Altyst computes these in exact decimal arithmetic, not with a language model, and clicking any number shows the formula behind it.