Commercial leases explained, from gross and net to CAM reconciliation

Commercial leases look complicated because they carry far more financial detail than a typical residential lease. Most of that complexity comes down to one question: who pays for what? Rent is only part of the answer. Property taxes, insurance, repairs and the cost of running shared areas all have to land somewhere.

This guide walks through the common commercial lease structures, explains how common area maintenance charges work and shows how the annual reconciliation process keeps estimates honest. It is general information, so have a commercial real estate attorney review your specific lease and a CPA review the accounting treatment.

The main commercial lease types

Gross lease

In a gross lease, sometimes called a full service lease in office buildings, the tenant pays a single rent amount and the landlord pays the operating expenses. The landlord builds expected costs into the rent. Tenants get predictability, and landlords carry the risk of rising expenses. Many gross leases still include a base year or expense stop, which passes increases above a starting level to the tenant.

Modified gross lease

A modified gross lease sits in the middle. Rent covers some expenses, and the tenant pays others directly. A common version has the tenant pay its own utilities and janitorial service while the landlord covers taxes, insurance and structural repairs. The exact split varies widely, so the lease language matters more than the label.

Single, double and triple net leases

Net leases shift operating costs to the tenant in layers:

• Single net (N): tenant pays base rent plus a share of property taxes.
• Double net (NN): tenant pays base rent plus taxes and building insurance.
• Triple net (NNN): tenant pays base rent plus taxes, insurance and common area maintenance.

A triple net lease is common in retail centers, freestanding single-tenant buildings and industrial space. Some markets use these terms a little differently, and an absolute net lease can push even roof and structural costs to the tenant.

Who pays what: a quick comparison

The table below shows a typical split. Your lease may differ.

Lease type	Property taxes	Building insurance	Common area maintenance	Tenant utilities
Gross (full service)	Landlord	Landlord	Landlord	Often landlord
Modified gross	Usually landlord	Usually landlord	Negotiated	Often tenant
Single net	Tenant share	Landlord	Landlord	Tenant
Double net	Tenant share	Tenant share	Landlord	Tenant
Triple net	Tenant share	Tenant share	Tenant share	Tenant

How CAM charges work

Common area maintenance, or CAM, covers the cost of operating spaces that all tenants share: parking lots, landscaping, lobbies, hallways, exterior lighting, snow removal, security and similar items. Depending on the lease, CAM may also include management fees and a share of property taxes and insurance, or those may be billed separately.

Each tenant pays a pro rata share, usually calculated by square footage. For example, a hypothetical tenant leasing 2,000 square feet in a 20,000 square foot center has a 10 percent share. If budgeted CAM for the year is $120,000, that tenant’s estimated share is $12,000, or $1,000 per month.

Lease language that shapes CAM charges:

• Inclusions and exclusions. Many leases exclude capital improvements, leasing commissions, costs for vacant space and expenses covered by insurance.
• Caps. Some leases cap annual increases in controllable expenses, such as landscaping or janitorial, while leaving uncontrollable items like taxes and insurance uncapped.
• Administrative fee. Landlords often add a percentage fee for managing CAM.
• Gross-up provisions. In a partly vacant building, variable costs may be adjusted as if the building were more fully occupied, so early tenants do not subsidize vacant space or underpay.
• Base year or expense stop. In gross and modified gross leases, tenants may pay only increases above a starting amount.

The annual CAM reconciliation

Because monthly CAM payments are estimates, the landlord compares them with actual costs after the year ends. This is the CAM reconciliation, sometimes called a true-up.

A typical reconciliation follows these steps:

1. Close the books for the year and total actual recoverable expenses by category.
2. Remove excluded costs and apply any caps, gross-up adjustments and admin fees.
3. Calculate each tenant’s share using the pro rata method in its lease.
4. Compare each tenant’s share of actual costs with the estimates it paid.
5. Send each tenant a statement showing the math, then bill the shortfall or credit the overpayment.
6. Update monthly estimates for the coming year.

Continuing the example above: if actual recoverable CAM came in at $132,000, the tenant’s 10 percent share is $13,200. It paid $12,000 in estimates, so it owes $1,200. If actual costs were $114,000, the tenant would receive a $600 credit.

Tip: Send reconciliations with supporting detail by category. Tenants who can see the math are far less likely to dispute the result or request a formal audit.

Avoiding common CAM disputes

Most disagreements trace back to vague lease language or surprises in the statement. To reduce friction:

• Define recoverable and excluded expenses precisely in the lease.
• Keep CAM expenses coded to separate accounts in your general ledger.
• Deliver reconciliations on time and in a consistent format.
• Respect audit rights and keep invoices organized and easy to share.
• Flag large one-time costs to tenants before they appear on a statement.

Managing commercial leases in software

Tracking lease types, pro rata shares, caps and estimates in spreadsheets works until it does not. Property management software with commercial lease support can store each tenant’s terms, bill monthly estimates automatically and help prepare reconciliations from your actual ledger. TenantLoop’s commercial tools support CAM alongside full property accounting, so recoveries tie back to the books. If you need a starting document, see our California commercial lease agreement, and have it reviewed by an attorney before use.