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Math-Based Rule

Base Year Error: How a Low Starting Number Costs You Every Year of Your Lease

Angel Campa, FounderCAMAudit
Last updated: April 2026

If your base year operating expenses were understated, every CAM reconciliation you have paid since lease signing has been inflated. A $10,000 base year understatement costs a 10% pro-rata tenant $1,000 per year for the life of the lease.

Definition

Base Year Error

A base year error in a commercial lease occurs when the operating expenses established for the base year are understated, causing tenants to pay charges above an artificially low starting point rather than above actual first-year costs. In leases with base year expense stops, tenants pay only for operating expenses that exceed the base year amount. When the base year expenses are set lower than the actual costs incurred in that period, such as due to vacancies, under-billing, incomplete records, or selective exclusion of cost categories, every subsequent year's charges are inflated by the same understated amount. CAMAudit's base year detection rule extracts the base year from the lease and the stated base year expense figure, then compares that figure against the actual operating expenses from the base year period when those records are provided. The tool calculates both the annual overcharge and the cumulative overcharge across the full lease term.

Key Takeaway

The base year sets the floor for every future CAM charge. A base year that is too low functions as a permanent overcharge that grows with each year's expenses.

How CAMAudit Detects This

CAMAudit extracts the base year from your lease and the base year expense amount if it is specified in the lease or a lease exhibit. CAMAudit then compares that figure to the actual operating expenses from the base year period, which you can upload as a separate reconciliation document for that year.

CAMAudit's base year detection rule calculates the annual overcharge when the base year expenses on file are lower than actual costs for that period: the difference between the correct base year amount and the stated base year amount, multiplied by your pro-rata share. Over a multi-year lease term, even a modest base year understatement results in significant cumulative overcharges.

CAMAudit also checks whether the landlord properly included all operating expenses in the base year calculation or selectively excluded cost categories to lower the baseline artificially. Selective exclusions that do not appear in the lease definition are a form of base year manipulation that CAMAudit flags.

Real-World Example

An office tenant signed a 7-year lease with a base year of 2022. The lease stated base year operating expenses of $18.50/sq ft. The actual 2022 operating costs available from building records were $21.20/sq ft. CAMAudit calculated the understatement: $2.70/sq ft. For a 3,500 sq ft tenant, this inflated every year's charges by $9,450 above what they should have been, totaling $66,150 in cumulative overcharges over the lease term.

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Related Guides

Dispute RecoveryDeep Dive
Base Year CAM Errors: How One Mistake Costs You for the Entire Lease
CAM OverchargesGuide
Base Year Error in Your CAM Lease: $120,000 Over 10 Years
IndustriesGuide
Law Firm Tenants: Base Year Errors Are the #1 CAM Overcharge in Class A Office Space
CAM ReconciliationGuide
Expense Stop vs. Base Year: Which Costs You More?

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Related Resources

Lease ClauseAudit Rights ClauseLease ClauseBase Year Stop ClauseScenarioAre My CAM Charges Too High? How to TellScenarioMy lease says CAM is capped but my charges went upResourcesCAM Line Items GuideResourcesTenant Type GuidesToolsFree CAM Audit Tools

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This page provides general educational information. It is not legal advice and may not reflect the most current law in your state. Consult a licensed attorney for advice specific to your situation.

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Recovery of past CAM overcharges depends on your specific lease terms, including any audit rights deadlines or ‘binding and conclusive’ provisions, and on applicable state law.

State statute of limitations periods apply to written contracts and range from 3 to 10 years. Your actual lookback window may be shorter based on your lease.

CAMAudit is a document analysis platform, not a law firm, and nothing on this site constitutes legal advice. Consult a licensed real estate attorney before initiating any dispute or legal proceeding.

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