What Is a Triple Net Lease? NNN Costs and Investor Risks

Information checked October 29, 2026. Examples use hypothetical US dollars, not current market quotes. The concept applies broadly; the contracts and company disclosures cited below are US examples, not universal legal rules. This is education, not individualized investment, legal, or tax advice.

What the three “nets” mean

A triple net lease, often written NNN, is a commercial property lease that generally assigns three groups of expenses to the tenant in addition to base rent: property taxes, building insurance, and maintenance or operating costs. The landlord owns the property; the tenant pays to use it under the lease.

The word “net” describes the allocation of expenses. It does not promise that every dollar of rent becomes the owner’s profit. The signed lease determines which bills the tenant must cover, which the landlord retains, and how charges are calculated.

For a real example, the 2013 Interphase lease, Section 3, explicitly calls itself a triple net lease and assigns property taxes, insurance premiums, and common-area expenses to the tenant beyond base rent. These charges can be called additional rent.

Expense category	What to look for in the lease
Property taxes	Which assessments are recoverable, how the tenant’s share is determined, and whether adjustments can be billed later
Building insurance	Which property insurance premiums are passed through, plus separate coverage the tenant must obtain
Maintenance and operating costs	Included services, common-area maintenance (CAM), repair duties, exclusions, and treatment of major replacements

Utilities can be separate too. A tenant’s own contents or liability insurance is not necessarily a substitute for the building-insurance charge. Avoid assuming “NNN” names every cost of occupying the space.

How NNN charges are paid

The tenant may pay some providers directly and reimburse the landlord for other bills. In a multi-tenant property, the contract may allocate a proportionate share of common costs, often linked to the space occupied. Read the formula: occupancy adjustments and other provisions can change a simple floor-area calculation.

The landlord may collect estimated expenses each month and later compare those collections with actual expenses. That reconciliation can result in an extra bill, a credit, or a refund, depending on the contract. Both the Interphase lease, Section 3 and the 2009 Extend Health lease, Section 7 use monthly estimates with annual reconciliation, but their deadlines and limits differ.

Those historical contracts illustrate possible arrangements, not current market rates or required US lease terms. In a proposed investment, request the actual lease, amendments, expense statements, and reconciliation history rather than relying on a listing’s three-letter label.

A worked example: rent quote vs. total tenant payment

Suppose a 2,000-square-foot shop has these quoted annual rates:

• Base rent: $20 per square foot per year.
• Estimated NNN charges: $6 per square foot per year.

Assume a full year of occupancy and that the tenant owes these charges without a cap or other adjustment. Separately billed utilities and other excluded costs are outside the example.

Component	Annual calculation	Annual amount
Base rent	2,000 × $20	$40,000
Estimated NNN charges	2,000 × $6	$12,000
Combined estimated payment	$40,000 + $12,000	$52,000

The combined monthly estimate is $52,000 ÷ 12 = $4,333.33, rounded to cents. Multiplying $26 by 2,000 gives an annual amount, not a monthly bill. Always check the units in a quote.

Now suppose the tenant’s recoverable expenses reconcile to $6.60 per square foot for that year. Its actual expense share is $13,200, so it owes $1,200 more than the $12,000 estimate, assuming the lease permits full recovery. Total annual payment becomes $53,200, before the separately excluded costs.

That is why an investor assessing a tenant’s ability to afford the space should look beyond base rent. Taxes, insurance, and operating bills can rise even when the base rent has not changed.

The landlord’s cash is a different calculation

The tenant’s $52,000 estimated payment is not $52,000 of property profit. Suppose the landlord collects it all and uses $12,000 to pay the corresponding recoverable expenses. That leaves $40,000 before costs the owner must bear.

Continue the example with these hypothetical annual amounts:

Landlord cash calculation	Amount
Base rent plus expense reimbursements collected	$52,000
Recoverable property bills paid	−$12,000
Other owner-paid property operating costs	−$2,000
Simplified net operating income (NOI)	$38,000
Loan payments, including principal and interest	−$24,000
Owner-funded capital work paid that year	−$8,000
Cash remaining before income tax and other excluded costs	$6,000

This illustration assumes full collection, no vacancy, and no other expenses. NOI is a property operating measure, not cash after financing and major capital needs. The loan payments and capital work reduce available cash but are not deducted in this simplified NOI calculation. Actual financial reports may define NOI differently.

Rexford Industrial’s 2025 annual report, “NOI and Cash NOI”, calculates NOI before interest and warns that the measure does not capture required capital spending or leasing commissions. Its disclosure makes the distinction explicit: even Cash NOI is not a measure of funds available for all cash needs.

Do not count reimbursements without their matching bills, or treat NOI as the amount you can withdraw. Nor is the $6,000 above an investment return percentage: calculating a return would also require the amount invested and a clear treatment of financing, taxes, and changes in property value.

Who pays for the roof and major repairs?

The NNN label does not answer this reliably. Read both the repair-duty clause and the expense-recovery clause. Who arranges the work and who ultimately pays can be different parties.

Two US contracts show the distinction:

• The Interphase lease, Section 3, assigns roof-replacement, foundation, and structural-soundness expenses to the landlord, even though ordinary roof repairs appear among operating expenses.
• The Extend Health lease, Sections 6–7, says the landlord maintains the roof and structural elements, but passes the cost through operating expenses. Capital repairs or replacements are spread over their useful lives, with recovery limited by the lease term.

Neither contract establishes what every NNN lease must say. More recent evidence also recognizes exceptions: Rexford’s 2025 annual report states that a triple-net landlord may retain duties to perform or pay for certain roof, structural, or building-system replacements.

For a beginner investor, the practical question is specific: “If this roof needs replacing next year, who must arrange it, who pays, and what limits apply?” A property inspection and a qualified local commercial real-estate lawyer’s review answer more than the listing label can.

Why investors use NNN leases, and what can go wrong

Assigning operating expenses to a tenant can reduce the landlord’s direct exposure to those bills while the tenant performs its obligations. But a contract allocates responsibility; it does not ensure payment or eliminate ownership risk.

Tenant default and vacancy

A tenant that cannot pay rent may also stop paying property expenses. When a single-tenant building becomes vacant, rent can stop while taxes, insurance, and maintenance continue. A long lease is useful only to the extent its obligations can be met and collected.

NNN REIT’s 2025 annual report discloses that tenant default or nonrenewal can cause vacancies, higher property expenses, and reletting expenditures. It also says a replacement lease may not achieve a comparable rent. These are company risk disclosures, not forecasts for a particular property or SEC endorsements.

Costs of finding the next tenant

A new occupant may require renovations, leasing commissions, or rent concessions. Ownership costs do not necessarily fall when rent revenue falls. Realty Income’s 2025 annual report describes these risks across its net-lease portfolio; that portfolio is broader than US triple-net leases alone.

The financial effect depends on the building, the market, the tenant, the financing, and the lease. There is no universal “safe” NNN yield or guaranteed vacancy period supported by these examples.

What to check before investing

Before treating a triple-net property as an income investment, work through the documents behind its advertised rent:

1. Read the complete agreement. Include amendments, renewal options, rent increases, expense definitions, and any tenant guarantees. Do not assume a parent company guarantees a subsidiary’s lease.
2. Check collections and tenant finances. Contracted rent is different from rent actually received. Ask what evidence supports the tenant’s ability to meet rent and expense obligations.
3. Identify retained costs. Check roof, structure, heating and cooling, insurance deductibles, major replacements, expense caps, and exclusions. Distinguish arranging repairs from paying for them.
4. Reconcile the numbers. Compare quoted estimates with actual expense statements. Include owner-paid costs, debt payments, and expected capital work in a cash budget.
5. Model a vacancy. Calculate how long you could fund loan payments and property bills without rent, including the cost of preparing the space for another tenant. Use property-specific estimates, not an assumed universal buffer.

If you are comparing rent income with other investments, our dividend-yield guide explains why an income-to-price ratio alone does not measure total investment return. Different assets have different obligations and risks; a high advertised income figure is not enough to compare them.

Direct property ownership is not the only route. The SEC’s REIT guide explains how investors can own shares in real-estate companies without buying buildings themselves. For a net-lease REIT, check what it actually owns and what its leases require. A lease’s allocation of expenses does not make either the building or the shares risk-free.