Common Area Maintenance charges cover the shared costs of operating a commercial property. Think parking lot maintenance, landscaping, exterior lighting, janitorial service for common areas, property insurance, property taxes, and similar expenses that benefit all tenants. As the property owner, you pay these costs upfront and pass them through to tenants based on what your lease agreements specify.

Each tenant’s share is calculated using their pro-rata percentage of the total leasable square footage. If a tenant occupies 2,000 square feet in a 20,000 square foot building, their pro-rata share is 10%. That means they’re responsible for 10% of all qualifying CAM expenses. This percentage gets established in the lease and typically stays fixed for the lease term unless usable space changes.

Monthly billing is based on estimates. At the beginning of the year, you project total CAM costs for the coming twelve months based on prior year actuals and any known changes like a new landscaping contract or a property tax increase. Multiply total estimated CAM by each tenant’s pro-rata share, divide by twelve, and that’s their monthly CAM charge. This gets billed alongside base rent.

The reconciliation happens after year-end when you know the actual numbers. Add up every qualifying CAM expense for the year and compare it to what you estimated. If actual costs were $120,000 but you estimated $110,000, tenants owe the difference based on their pro-rata share. If actuals came in under estimates, tenants get a credit. Most leases require you to complete reconciliation within 90 to 120 days after year-end and send tenants a detailed statement showing estimated versus actual figures.

Tracking CAM expenses throughout the year is where the bookkeeping matters most. Every qualifying expense needs to be categorized correctly and kept separate from non-CAM property costs. Commercial real estate investors with multiple properties need a chart of accounts that isolates CAM-eligible expenses by property. If you lump everything together, reconciliation becomes a painful sorting exercise instead of a simple report.

Keep in mind that most commercial leases give tenants the right to audit your CAM records. This means your documentation needs to hold up to scrutiny. Save invoices for every CAM expense. Make sure vendor payments tie back to specific properties. If a tenant’s accountant asks to review your books, you should be able to produce organized records that clearly support every dollar you billed.

Not all expenses qualify as CAM pass-throughs. Your lease defines what’s included, and leases vary. Capital improvements are usually excluded or amortized over their useful life rather than passed through in a single year. Management fees may or may not be included depending on lease language. Read your leases carefully and track expenses accordingly.

If you own commercial property and handle your own books, set up dedicated expense categories for CAM-eligible costs from day one. Trying to reconstruct a full year of CAM expenses from a general ledger that wasn’t designed for it wastes time and introduces errors. Working with Phoenix bookkeepers who understand commercial property accounting can save you from reconciliation headaches and protect you if a tenant ever exercises their audit rights.