A CAM audit is a formal review of a landlord's CAM reconciliation statement to verify that charges are accurate, properly calculated, and consistent with the lease. The audit compares the statement line items against the lease's expense definition, pro-rata share formula, gross-up provision, and any caps.

How long does a CAM audit take?

With CAMAudit, a full forensic audit runs in under 15 minutes. Traditional CPA-led audits take 4 to 8 weeks and require scheduling, document collection, and manual review. The speed advantage of CAMAudit comes from automating the extraction and detection steps.

What documents do I need for a CAM audit?

You need your commercial lease (including all addenda and exhibits) and your CAM reconciliation statement from your landlord. The reconciliation is usually sent annually, within 90 to 120 days after the close of the lease year. If you haven't received it yet, request it in writing.

What does a CAM audit actually check?

CAMAudit checks 14 categories: management fee overcharge, pro-rata share error, gross-up violation, CAM cap violation, base year error, controllable expense cap overcharge, estimated payment true-up error, gross lease charges, excluded service charges, insurance overcharge, tax overallocation, utility overcharge, common area misclassification, and landlord overhead pass-through.

Do I need an attorney to dispute CAM charges?

Not necessarily. CAMAudit generates a dispute letter draft grounded in your specific findings and lease language. Many tenants resolve CAM disputes by sending this letter directly to their landlord or property manager. For large disputes or adversarial landlords, involving an attorney is advisable.

Case Study: 12% Pro-Rata Inflation That Cost a Tenant $4,500 Per Year

The math looked right. That was the problem. An accounting firm in a suburban Ohio office park had been receiving CAM reconciliation statements for four years that were internally consistent, professionally formatted, and arithmetically correct — given the denominator the landlord was using.

The denominator was wrong.

The Scenario

The firm occupied 4,800 square feet in a suburban office park in Ohio. Their lease identified the property's total rentable area as 48,200 square feet — the figure that anchors their pro-rata share calculation.

Total annual CAM costs for the property ran approximately $140,000. Under the lease's terms, the firm's correct pro-rata share was:

4,800 ÷ 48,200 = 9.96%

Their correct annual CAM allocation: $140,000 × 9.96% = $13,944

That's what they should have been paying. That's not what they were paying.

What Triggered the Audit

Four years into the lease, the firm's CFO ran a back-of-envelope check on their CAM bill. The office park had two vacant suites — she knew this because she'd seen the "For Lease" signs — but their CAM bill had not gone down. It had gone up.

That made no sense under a gross-up provision. But they didn't have a gross-up clause. She uploaded the lease and four years of CAM statements to CAMAudit.

What CAMAudit Found

Rule 4 — Pro-Rata Share Error — flagged the issue immediately.

The landlord's spreadsheet was using 42,500 square feet as the denominator. Not 48,200. The 42,500 figure represented only the currently occupied space — it excluded the two vacant suites and a storage unit with a non-paying holdover tenant.

The lease said "total rentable area of the Building," which is 48,200 square feet. Full stop. Vacant or not.

By shrinking the denominator to occupied-only space, the landlord had inflated every tenant's pro-rata share. The accounting firm's share went from 9.96% to:

4,800 ÷ 42,500 = 11.29%

That's a 12% inflation in their share — applied to every line item in the CAM pool, every year, for four years.

40% of CAM reconciliations contain material errors (Tango Analytics/PredictAP, 2023)

The Math

	Correct	Billed	Difference
Denominator (sq ft)	48,200	42,500	—
Pro-rata share	9.96%	11.29%	+1.33 points
Annual CAM (property)	$140,000	$140,000	—
Annual tenant allocation	$13,944	$15,806	+$1,862/yr

Four years of overcharges: $1,862 × 4 = $7,448 total

The per-year gap sounds modest — under $2,000. But it compounds. And it applies to every CAM charge simultaneously: janitorial, landscaping, insurance, utilities, parking lot maintenance. Every line was inflated by the same 12% factor.

"Pro-rata denominator errors are some of the easiest overcharges to miss because the individual line items still look reasonable. You'd have to know the correct denominator to catch it — and that number lives in a lease exhibit most tenants never open after signing." — Angel Campa, Founder of CAMAudit

The Resolution

The firm's audit rights clause allowed a 3-year lookback. Ohio's statute of limitations on contract claims extends to six years, but the lease's specific audit rights language capped the formal reconciliation period at three years from the date of the written audit request.

They sent a dispute letter citing the lease's rentable area definition, attaching the relevant lease exhibit showing the 48,200 square foot figure, and providing the side-by-side calculation of correct vs. billed pro-rata share.

The landlord acknowledged the error. No pushback on the math — the lease exhibit was unambiguous. They corrected the denominator going forward and issued a credit for the three-year lookback period:

$1,862 × 3 years = $5,586 credit

The fourth-year overcharge (outside the audit rights window) was forfeited. That's $1,862 lost permanently — which is why filing an audit rights request as soon as an issue is suspected matters.

Key Takeaway

The pro-rata denominator is a number that appears in your lease, usually in an exhibit or a definitions section. It is not a number the landlord gets to recalculate based on current occupancy — unless your lease specifically authorizes that.

Two things to verify immediately:

Find your denominator in the lease. It's usually defined as "total rentable area," "gross leasable area," or a specific square footage number in an attached exhibit. Write it down.
Compare it to what's on your CAM statement. Ask the landlord to show you the denominator used in your reconciliation calculation. If they won't provide it, that's a red flag.

Occupied-only denominators are a common error — sometimes inadvertent, sometimes not. Either way, the overcharge is real and recoverable.

For a deeper look at the math, see pro-rata share errors: the math.

Frequently Asked Questions

What square footage figure should a landlord use as the pro-rata denominator?

It depends on your lease. Most commercial leases define the denominator as the total rentable area or gross leasable area of the building or property — a fixed number regardless of occupancy. Some leases include a gross-up provision that allows the landlord to adjust the expense pool when occupancy falls below a threshold, but that is a different mechanism from shrinking the denominator. If your lease does not include an occupancy adjustment clause, the denominator is the number in your lease, period.

What if the landlord says the denominator was corrected in a later amendment?

Ask to see the amendment. Any change to the rentable area definition or pro-rata share calculation method requires a signed lease amendment — verbal assurances or email confirmations are not sufficient to override original lease terms in most commercial jurisdictions. If there is an amendment, it should be dated, signed by both parties, and specify the effective date of the change. CAMAudit's audit rights output will reference the controlling document version.

Can I recover overcharges caused by a denominator error going back more than three years?

It depends on two things: your lease's audit rights clause and your state's statute of limitations. The audit rights clause typically controls how far back you can formally request a reconciliation correction from the landlord. Your state's SOL governs how far back you could go in litigation if the landlord refuses to cooperate. In this Ohio case, the lease capped the recovery at three years even though Ohio's contract SOL is longer. Always check both — and file your audit request as soon as you identify the issue.

Case Study: 12% Pro-Rata Inflation That Cost a Tenant $4,500 Per Year