A triple net lease, usually written as NNN, is a commercial lease where the tenant pays base rent plus three categories of property expenses on top: property taxes, building insurance, and maintenance. Those three expense categories are the “nets,” and they shift most of the cost of running the building from the landlord to the tenant. In exchange, the quoted base rent is lower than it would be under a gross lease, but your real monthly cost can be far higher than the per-square-foot number on the listing suggests.
A space advertised at $18 per square foot NNN can land closer to $28 once the three nets are added in. Before you sign, and before you compare one property to another, you need to know what each of those nets actually covers, how your share is calculated, and which clauses in the lease determine whether you absorb a surprise six-figure repair bill or hand it back to the landlord.
What the Three Nets Cover
Each net works differently and carries its own risk.
Property Taxes
Property taxes are the local tax rate multiplied by the property’s assessed value, and depending on the jurisdiction you may see city, county, and school district rates stacked on one bill along with line items for services like fire protection or solid waste. These assessments are usually the single largest piece of your NNN charges.
Most NNN leases require you to pay the tax bill in full, or reimburse the landlord within a set window after it’s issued. Some leases use a different structure: the landlord covers the first year’s taxes and you pay only the increases above that baseline in later years. Government assessments for infrastructure like sewer upgrades or street lighting usually fall under this net too. Taxes can jump sharply after a reassessment or a new local budget, so looking at the property’s tax history before you sign tells you where costs are heading. Failing to pay is a lease default that can trigger eviction or a lawsuit for the debt.
Building Insurance
The second net covers property and casualty insurance on the building. The landlord typically holds the master policy because their lender requires it, but the premium passes through to you. Rates depend on the building’s age, construction, location, and claims history.
Beyond funding the building policy, most NNN leases require you to carry your own general liability insurance, often with minimum limits of $1 million per occurrence, and to provide proof of coverage every year. Letting a policy lapse counts as a lease default. The landlord’s policy covers the structure but almost never covers your equipment, inventory, or improvements, so you need a separate business personal property policy for those. Business interruption coverage is also worth carrying; a common benchmark is enough to replace twelve months of lost revenue plus six months of extended recovery.
Maintenance and Common Area Costs
Common area maintenance, or CAM, is the broadest and least predictable net. It covers parking lot repairs, landscaping, snow removal, exterior lighting, elevator servicing, janitorial work in shared hallways, and similar items. In a multi-tenant property these costs are pooled and split among tenants based on each tenant’s share of the leasable space. Interior systems inside your own space, like plumbing, electrical, and HVAC, are usually your direct responsibility.
Most landlords add a management or administrative fee on top of CAM to cover vendor coordination and property management. These fees generally run from about 4% to 15% of total operating expenses. On a large property that percentage adds up quickly, and it is worth asking exactly what it covers and whether it’s negotiable.
How NNN Compares to Other Commercial Leases
The “net” label tells you how many expense categories transfer from landlord to tenant. The differences matter when you’re comparing quoted rents.
- Gross lease: one flat rent. The landlord pays taxes, insurance, maintenance, and often utilities out of that rent.
- Single net (N): base rent plus property taxes only.
- Double net (NN): base rent plus property taxes and insurance.
- Triple net (NNN): base rent plus taxes, insurance, and maintenance.
- Absolute net: a step beyond standard NNN, where the tenant pays every expense without exceptions, including structural repairs and roof replacements.
Because of the gap between quoted base rent and real occupancy cost, a gross lease at $30 per square foot can easily end up cheaper than an NNN lease quoted at $20. Always ask the landlord or broker for the estimated NNN charges, in dollars, before putting one property against another.
Standard NNN vs. Absolute NNN
This distinction catches a lot of tenants off guard. In a standard NNN lease, the landlord usually keeps responsibility for major structural repairs: the foundation, load-bearing walls, and often the roof structure itself. You handle operating costs and day-to-day maintenance, but if the foundation cracks, that’s the landlord’s problem.
An absolute net lease, sometimes called a bondable lease, removes that safety net. The tenant pays for everything, structural repairs and full roof replacements included. These leases are designed so the landlord’s income is untouched by any property expense, which is why institutional investors favor them and why national chains with strong credit tend to be the ones signing them.
The practical gap is enormous. A standard NNN tenant facing a $200,000 roof replacement can point to the lease and send the bill back to the landlord. An absolute NNN tenant writes the check. The label “NNN” by itself does not tell you which version you are looking at, so read the structural-repair and roof clauses carefully.
How Your NNN Bill Is Calculated
Your total occupancy cost has two parts: base rent, which is fixed or increases on a set schedule, and additional rent, which covers your share of the three nets and fluctuates each year.
Your Pro Rata Share
In a multi-tenant building, your share of operating expenses tracks the space you occupy relative to the total leasable area. Lease 5,000 square feet in a 20,000-square-foot shopping center and your pro rata share is 25%: you pay 25% of the property tax bill, 25% of insurance premiums, and 25% of CAM.
Watch how the lease defines “total leasable area.” Some landlords use the full building footprint; others exclude certain spaces from the denominator. A smaller denominator gives you a larger percentage even though your actual space hasn’t changed.
Monthly Estimates and Year-End Reconciliation
Landlords project the coming year’s expenses and bill you monthly estimates alongside your base rent. At year end they reconcile estimates against actual costs. Overpayment usually becomes a credit against future rent. Underpayment becomes a reconciliation bill, typically due within 30 to 60 days.
These bills can be surprisingly large in a year when taxes jump or a major repair hits. Budgeting a cushion above your monthly estimates is smart, especially in year one when you have no history to work from.
Base Year and Expense Stop Methods
Some leases use a base year instead of passing through 100% of expenses from day one. The landlord absorbs operating expenses at the first-year level, and in later years you pay only the amount by which expenses exceed that base. An expense stop works the same way, set as a dollar amount per square foot: you pay only what runs over the threshold. Both methods give the tenant a floor of protection and make year-one costs predictable. Both also reward you for negotiating in a year when expenses happen to be high, since a higher baseline means smaller pass-throughs later.
Capital Expenditures vs. Routine Maintenance
One of the most common NNN disputes is whether something counts as a repair, which is on you, or a capital improvement, which may be the landlord’s responsibility or at least billed differently. Replacing a few shingles is maintenance. Replacing the entire roof is a capital expenditure. The line blurs fast.
Well-drafted leases handle capital expenditures by amortizing them over the useful life of the improvement rather than billing the full cost at once. A $30,000 roof replacement with a 39-year useful life works out to about $770 per year, and in a multi-tenant building that annual figure then splits across tenants by pro rata share. The key is making sure the lease specifies amortization as the method. Without that language, you can face a demand for your full share of a six-figure repair in a single billing cycle.
Under an absolute NNN lease the tenant carries the full cost of capital expenditures regardless of how they’re billed. Under a standard NNN, major structural work generally stays with the landlord, but the exact lease language controls.
What to Negotiate Before You Sign
The clauses you negotiate up front determine your real exposure over a five- or ten-year term.
Expense Caps
An expense cap limits how much your NNN charges can rise year to year, often between 3% and 5%. Many leases distinguish between controllable expenses (landscaping, janitorial, general maintenance, administrative fees) and uncontrollable ones (property taxes, insurance premiums). Landlords are generally more willing to cap controllable expenses because they can manage those costs. A cap limited to the controllable portion still protects you from a landlord who decides to upgrade the landscaping contract on your dime.
Audit Rights
Your right to verify what you’re being charged is one of the most important clauses in a NNN lease, and tenants routinely let it expire. Most leases let you, or an accountant you hire, review the landlord’s books and invoices for the expenses passed through to you. The window to request an audit typically runs 30 to 180 days after you receive the annual reconciliation statement. Miss it and you may lose any right to challenge overcharges for that year.
If an audit finds errors, the lease usually requires you to raise the dispute quickly, sometimes within 30 days of completing the audit. Billing errors happen more often than tenants expect, particularly with administrative fees and CAM allocations in multi-tenant buildings. Calendar the reconciliation deadline the day you sign the lease.
SNDAs and Estoppel Certificates
Two documents protect your lease if the property changes hands. A Subordination, Non-Disturbance, and Attornment Agreement (SNDA) is signed by you, the landlord, and the landlord’s lender. The non-disturbance piece guarantees that if the landlord is foreclosed on, the new owner or the bank must honor your lease for its remaining term. Without one, foreclosure can wipe out your lease. SNDAs are standard but not automatic; request one at lease signing.
When a landlord sells the property, the buyer will ask you to sign an estoppel certificate confirming your rent, expiration date, prepaid rent or deposits, and whether either side is in default. The certificate is legally binding; once you sign it, you cannot later claim the lease terms were different. Read it carefully, and correct errors about rent, renewal options, or landlord obligations before you sign. Anything you let through becomes the official record.
Tax Treatment of NNN Payments
Payments you make toward NNN expenses are generally deductible as business expenses. Federal law allows a deduction for “rentals or other payments required to be made as a condition to the continued use or possession” of business property.1Office of the Law Revision Counsel. 26 U.S. Code 162 – Trade or Business Expenses The IRS treats property taxes paid by a tenant under a lease as additional rent, deductible in the year paid for cash-basis taxpayers or the year the liability is established for accrual-basis taxpayers.2Internal Revenue Service. Publication 535 – Business Expenses Insurance premiums and maintenance costs paid as lease obligations follow the same ordinary-and-necessary business expense rules.
If you fund improvements to the leased space, depreciation depends on who owns them. Tenant-funded leasehold improvements that qualify as “qualified improvement property,” such as interior renovations, new HVAC systems, fire alarms, or security systems, can be depreciated over 15 years.3Internal Revenue Service. Instructions for Form 4562 – Depreciation and Amortization Depending on the cost, you may be able to expense the full amount immediately under Section 179 or bonus depreciation rules instead of spreading it over 15 years. These limits change often, so confirming current-year rules with a tax advisor before a major buildout is worth the conversation.