Triple net (NNN) leases, explained in plain English

Updated October 27, 2026 · General information, not legal advice.

If a landlord quotes you a rent like "$2.25 per square foot, NNN," the number you see is not the number you will pay. A triple net lease splits your monthly cost into two parts: base rent, and your share of the building's operating costs. This guide walks through what "net" means, how the extra charges are calculated, and the questions worth asking before you sign.

How to use this guide: read it with your own lease or proposal open beside you. Lease labels and "standard" terms vary from property to property and from landlord to landlord, so treat everything here as a list of things to look for and questions to ask, not as a description of what your document says. When a section of your lease is unclear, ask the landlord or its representative to explain it in writing, and keep notes of what was agreed.

What the three "nets" are

In a NNN lease, the tenant pays base rent plus a share of three categories of property costs that a landlord would otherwise absorb:

Property taxes. The real estate taxes assessed on the land and building, divided among tenants.
Building insurance. The landlord's property and liability insurance on the building (separate from the insurance you carry for your own business).
Common area maintenance (CAM). The cost of operating and maintaining shared areas: parking lot sweeping and repair, landscaping, common lighting, exterior maintenance, trash enclosures, and often property management fees.

Together these are often called "NNN charges," "operating expenses," or "additional rent." The exact list depends entirely on how your lease defines them, which is why the definitions section matters so much.

How your share is calculated

Most NNN leases use a "pro rata share." That is usually your suite's square footage divided by the total leasable square footage of the building or center. If you lease 1,500 square feet in a 30,000-square-foot center, your pro rata share would be 5%, and you would pay 5% of the property's taxes, insurance, and CAM.

Check two things here. First, confirm the square footage numbers in the lease match what you are actually getting. Second, look at whether the denominator is the whole property or only the leased portion. Some leases divide by the occupied space only, which means your share rises when neighbors move out.

Estimates now, true-up later

You usually do not pay NNN charges as one bill. Instead, the landlord estimates the year's costs and bills you a monthly amount alongside base rent. After the year ends, the landlord compares the estimate to actual costs and sends a reconciliation, sometimes called a true-up. If actual costs were higher, you owe the difference. If they were lower, you should get a credit or refund.

This is where small tenants get surprised. A low estimate makes a space look cheaper during the tour, and the catch-up bill arrives months later. Before signing, ask for the last two or three years of actual NNN costs for the property, not just the current estimate. A history tells you far more than a single number.

What "NNN" does not mean

Lease labels are not standardized. One landlord's "NNN" lease may make you responsible for your own HVAC repairs and replacement, while another keeps roof and structure with the landlord. Some leases called "NNN" pass through capital replacements like a new roof or parking lot resurfacing. Others exclude them or spread them out over their useful life. The label tells you the general idea; the lease language tells you the actual deal.

Costs worth reading closely

These items commonly cause disputes or surprises in small-tenant NNN leases:

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Capital expenses. Is a roof replacement or parking lot repaving passed through all at once, amortized over years, or excluded?
Management fees. Is there a management or administrative fee, and how is it calculated (for example, a percentage of CAM or of gross rents)?
Property tax reassessment. In some states, a sale of the property can trigger a tax reassessment. Look for whether increases from a sale are passed through to tenants.
HVAC. Who maintains, repairs, and replaces the unit serving your space? Replacement can be a significant expense.
Caps. Some leases cap annual increases in "controllable" CAM costs. Ask whether a cap is available and which costs it covers.
Audit rights. Do you have the right to review the landlord's records, and how long do you have to raise a dispute after the reconciliation arrives?

How to compare NNN with other lease types

To compare a NNN space with a gross or modified gross space, convert everything to a total monthly occupancy cost: base rent, plus estimated NNN charges, plus anything else you would pay directly (utilities, janitorial, your own insurance). Then compare totals, not base rents. Our gross vs. modified gross lease guide explains the other common structures. The free move-in cost calculator can help you add up the upfront costs too.

Questions to ask before you sign

What were the actual NNN costs per square foot for the last two to three years?
What is my pro rata share, and what square footage is used to calculate it?
Which expenses are excluded from CAM?
Are capital improvements passed through, and if so, how?
Is there a cap on increases in controllable expenses?
When will I receive the annual reconciliation, and how long do I have to review it?
Who is responsible for HVAC repair and replacement?

For more on reviewing the operating cost side, see our CAM charges guide.

Frequently asked questions

Is a NNN lease bad for a small tenant?

Not necessarily. NNN is very common for retail and industrial space. It shifts cost risk to the tenant, so the key is understanding the history of the charges, the exclusions, and any caps before you commit.

Can NNN charges go up during my lease?

Yes. Because they reflect actual costs, they can rise with taxes, insurance premiums, and maintenance. Caps on controllable expenses, if negotiated, can limit some increases.

Do I still need my own insurance in a NNN lease?

Usually yes. Paying a share of the landlord's building insurance typically does not cover your own business, inventory, or liability. Most leases require you to carry your own policies.