5 common modified gross lease overcharges (and how to catch them)
You signed a modified gross lease. The landlord covers operating expenses up to the base year level. You pay increases above it. The structure is supposed to limit your exposure.
Then the reconciliation arrives.
The total looks higher than it should. The math on the summary page checks out. But the summary page is not where the errors live.
According to Tango Analytics (cited by PredictAP, February 2026), 40% of CAM reconciliations contain material billing errors. BOMA puts it at up to 30%. These figures span all commercial lease types, but modified gross leases have specific structural vulnerabilities that create their own error patterns. The expense stop baseline, the management fee cap, the insurance cost definitions, and the utility billing methodology are each a place where overcharges accumulate quietly year after year.
These are the five patterns CAMAudit's detection engine catches most often in modified gross lease reconciliations, with the dollar math behind each.
40% of CAM reconciliations contain material billing errors across all commercial lease types (Tango Analytics, 2023)
For a complete guide to how modified gross leases work, see the Modified Gross Lease Guide. For all 14 detection rules with worked examples across lease types, see the commercial lease CAM overcharge guide.
Modified gross leases create structural overcharge vulnerabilities that are invisible on the reconciliation summary. The five patterns below require requesting the general ledger, base year occupancy records, and insurance policy backup to verify.
1. Excluded expense categories billed anyway
In a modified gross lease, some operating expenses are typically assigned to the landlord permanently, not just up to the base year amount. Property taxes are a classic example in office leases where the lease structure separates tax treatment from other operating expenses. Insurance is another. So are structural repairs and executive-level property management overhead.
When a management company changes, when a property is sold, or when a new billing system is configured, these landlord-responsibility items sometimes migrate into the reconciliation. The tenant receives a bill that includes line items their lease does not authorize.
This is the most common single-category error in the Tango Analytics/PredictAP (February 2026) analysis of 40% error rates. It is also the easiest to catch if you know what your lease says. For the full framework on excluded categories, see excluded service charges in CAM statements.
Dollar example:
Tenant space: 6,000 SF. Building: 80,000 SF. Pro-rata share: 7.5%.
Annual property tax for the building: $320,000. Assigned to landlord under the lease.
Landlord's reconciliation includes taxes anyway. Tenant's allocated share: $320,000 times 7.5% equals $24,000.
If this error ran for 3 years before being caught, the recoverable overcharge is $72,000, plus any escalations in the tax bill during that period.
How to catch it: Pull the operating expense definition from your lease. List every category in the reconciliation. Any category not included in the lease's defined pass-through pool is potentially unauthorized. Excluded items are most often labeled with generic terms like "building expenses" or "operating costs" that obscure the underlying category.
2. Inflated or un-grossed expense stop base year
This is the structural overcharge that makes modified gross leases uniquely vulnerable. When the base year is established during a period of low occupancy, the variable operating expenses recorded in that year are artificially depressed. Janitorial, utilities, and HVAC all scale with building occupancy. A building at 35% occupancy costs much less to operate than the same building at 90% occupancy.
When that low-occupancy year is used as the baseline without adjustment, every future reconciliation charges the tenant for the difference between actual costs and the suppressed baseline, even when that difference reflects normal stabilized building operations rather than real cost growth.
The compounding formula: if the base year variable expense was V0 and the correctly grossed-up figure is V*, the tenant pays s times (V* minus V0) every year, where s is their pro-rata share. On a 10-year lease with a $45,000 annual overcharge from this error: $450,000 in total excess payments.
The industry standard for correcting this, documented in published practitioner guidance and SEC-filed office lease forms, is a gross-up to 95% occupancy for variable expense categories. BOMA's lease guidance references this standard. A publicly filed standard-form modified gross office lease (SEC EDGAR, 2004) uses a 95% trigger concept for variable expense gross-up.
BOMA's research puts the rate of material reconciliation errors at up to 30% across the industry. Base year gross-up errors are a primary contributor to that figure in office markets.
Dollar example:
Base year building occupancy: 38%. Actual variable expenses in base year: $410,000. Grossed-up variable expenses at 95%: $680,000. Suppression: $270,000.
Tenant pro-rata share: 8%. Annual overcharge: $270,000 times 8% equals $21,600.
Over an 8-year lease: $172,800.
How to catch it: Request the building's occupancy rate for the base year. If it was below 90%, request the landlord's gross-up calculation and compare the grossed-up figure to the actual base year amount. The difference multiplied by your pro-rata share is your annual overcharge.
30% of material CAM reconciliation errors in office markets stem from base year gross-up errors or suppressed expense stop baselines (BOMA, 2023)
3. Management fee exceeding lease limit
Most modified gross leases specify a cap on the property management fee that can be included in the operating expense pool. The AIR CRE standard commercial lease form uses 5% as the management fee benchmark, and the 3-5% range appears widely in published commercial leasing guidance as the standard market range.
When the landlord bills above the lease cap, or when the fee calculation includes an improper base, the tenant overpays on every year's reconciliation.
Two distinct error patterns appear here:
Rate overcharge: The lease caps the fee at 4%. The landlord bills 6%. The overcharge is straightforward to calculate once detected.
Fee-on-fee: The management fee is calculated as a percentage of the total CAM pool, and that pool already includes the management fee. The landlord is charging a percentage on a base that includes itself. Most lease provisions define the management fee base as controllable expenses or revenues, neither of which includes the management fee.
Dollar example:
Building total controllable operating expenses: $2,000,000. Lease cap: 5% management fee.
Authorized management fee: $2,000,000 times 5% equals $100,000.
Landlord bills 15% management fee: $2,000,000 times 15% equals $300,000.
Overcharge: $200,000 for the full building. Tenant's 8% pro-rata share: $16,000 per year.
Over a 7-year lease: $112,000.
Note: a 15% management fee is not uncommon when the landlord uses an affiliated management company billing at a non-arm's-length rate. Fees to affiliated entities require the same cap analysis as fees to third parties.
How to catch it: Locate the management fee provision in your lease. Note the cap percentage and the defined base. Multiply the authorized base by the cap rate. Compare to the billed management fee. If the billed amount is higher, request the calculation backup.
4. Insurance overcharges
Property insurance is a legitimate pass-through in most modified gross leases. The problem is not the category; it is what gets billed under it.
Several specific insurance overcharge patterns appear in modified gross lease reconciliations:
Broker commissions retained by the insurer or the landlord's affiliate. Insurance premiums include a broker commission built into the quoted rate. When the broker is the landlord's affiliate and commissions are rebated back to the landlord, the tenant is effectively paying for the landlord's insurance revenue, not just the landlord's insurance cost. An English court addressed this directly in London Trocadero [2015] LLP v Picturehouse Cinemas Limited [2025] EWHC 1247, ruling that a landlord was not entitled to recover insurance rent representing commissions rebated to itself. The principle applies whether the court is in London or New York: billing inflated insurance costs that include a self-directed rebate is a recoverable overcharge.
Terrorism, flood, or earthquake riders not permitted by the lease. If the lease defines insurable property risks and the landlord purchases additional coverage for perils not included in that definition, the premium for those additional coverages is not a tenant obligation. Terrorism insurance riders, flood coverage for non-flood-zone properties, and earthquake riders where the lease is silent on seismic coverage are common examples.
Portfolio-level insurance billed at property-level. When a landlord insures multiple properties under a blanket policy, the allocation of premium to any individual property is discretionary. Some landlords allocate premiums that reflect portfolio risk rather than the specific risk profile of your building. The result is that a low-risk suburban office building bears insurance costs that reflect a higher-risk portfolio mix.
Commercial property insurance premiums surged across 2022 through 2025, making insurance a high-dollar line item in reconciliations from that period. That surge also means any allocation error in insurance is more expensive now than it would have been in 2020 or 2021.
Dollar example:
Building annual insurance premium (legitimately allocated): $85,000. Landlord bills: $112,000. Excess includes $18,000 in terrorism rider premium and $9,000 in broker commission rebate.
Tenant's 8% pro-rata share of the overcharge: ($112,000 minus $85,000) times 8% equals $2,160 per year.
Over 6 years: $12,960. Not enormous on its own, but compounded with the other four categories on this list, the total often clears $50,000.
How to catch it: Request the insurance certificate and the actual policy premium breakdown. Compare the billed amount to the actual premium net of commissions. Verify the coverage types listed on the policy against the lease's insurance definition.
5. Utility overcharge
Utilities billed through the CAM pool in a modified gross lease should reflect actual utility provider costs allocated fairly by metered usage or a reasonable square footage formula. Two overcharge patterns appear here.
Billing above the actual utility provider rate. The landlord receives a bulk electricity or gas rate from the utility provider, then re-bills tenants at a higher per-unit rate, capturing a margin. This is not permitted unless the lease specifically authorizes a re-billing markup. The U.S. Energy Information Administration reports that commercial building electricity expenditure runs roughly $1.44/sqft nationally. Properties billing significantly above that figure warrant a rate verification against the actual utility invoices.
Double-billing through the CAM pool. In some buildings, each tenant pays their own electricity directly through a submeter, but the landlord also includes common area utility costs in the CAM pool. The issue arises when the CAM pool includes utility costs for spaces that are individually metered, effectively charging tenants twice for the same electricity. CAMAudit's detection engine flags utility line items in the CAM pool when submeter billing is confirmed by the lease.
Dollar example:
Actual utility provider rate: $0.11/kWh for the building's commercial rate. Landlord re-bills common area electricity at $0.16/kWh. Building common area electricity: 180,000 kWh/year.
Total utility pool: $0.16 times 180,000 equals $28,800. Actual cost: $0.11 times 180,000 equals $19,800.
Overcharge in the pool: $9,000. Tenant's 8% share: $720/year.
Over 10 years: $7,200 from this one line item.
How to catch it: Request the utility provider invoices for common area accounts. Compare the per-unit rate billed in the CAM reconciliation to the rate on the provider invoices. For buildings where tenants have individual submeters, confirm that utility costs for submetered spaces are excluded from the CAM pool.
Running all five checks
These five patterns are not hypothetical. After testing reconciliation samples from published audit cases through CAMAudit, the most common finding is that two or three of these patterns appear simultaneously in the same reconciliation. No single error is huge in isolation. Combined, they can represent $20,000 to $80,000+ in annual overcharges for a mid-size office tenant.
The reconciliation summary you receive does not show any of this. It shows a total number and a few categories. Getting to the errors requires requesting the general ledger detail, the insurance policy backup, the management fee calculation, and the base year occupancy records.
That is exactly what a CAM audit does.
For related reading on how property management software generates these errors systematically, see CAM errors from property management software. For what to do after finding overcharges, see excessive CAM charges: recovery process.
FAQ
How do I know if my modified gross lease has an overcharge?
The reconciliation summary will not tell you. You need to verify the expense categories against your lease's pass-through definition, check the management fee rate against the cap in your lease, confirm the base year occupancy and gross-up calculation, and request backup documentation for the insurance and utility line items. Most overcharges are invisible at the summary level.
Is a management fee above the lease cap automatically an overcharge?
Yes. The lease cap is the ceiling for what the landlord can include in the CAM pool for management fees. Billing above the cap is a breach of the lease, regardless of what the landlord paid their management company. The issue is more common when the landlord uses an affiliated management company.
What documentation should I request to verify my reconciliation?
At minimum: the building's operating expense general ledger for the reconciliation year, the base year operating expense detail with occupancy records, the insurance certificate and policy premium breakdown, the management fee calculation showing the rate and base, utility provider invoices for common area accounts, and the pro-rata share denominator with total leasable area documentation.
What is the statute of limitations on disputing a modified gross lease overcharge?
It varies by state. Texas provides 4 years for written contract claims. California provides 4 years under Code of Civil Procedure section 337. New York provides 6 years under CPLR section 213. Illinois provides 10 years for written contracts under 735 ILCS 5/13-206. The clock typically starts when the overcharge was assessed, meaning when the reconciliation was delivered.
Frequently Asked Questions
What are the most common overcharges in modified gross leases?
The five most common overcharge patterns are: (1) excluded expense categories billed anyway, particularly after property sales or management company changes; (2) un-grossed base year variable expenses that suppress the baseline and create phantom increases; (3) management fees billed above the lease cap or calculated on an improper base; (4) insurance overcharges including broker commission rebates and non-permitted coverage riders; and (5) utility costs billed above the actual provider rate or double-billed through the CAM pool.
How does an un-grossed base year create a compounding overcharge?
When the base year is established during low occupancy, variable expenses like janitorial and utilities are artificially low. That suppressed figure becomes the permanent baseline. Each year, the tenant pays their pro-rata share of the difference between the suppressed baseline and actual stabilized costs. The formula is: annual overcharge equals pro-rata share times (grossed-up base year expenses minus actual base year expenses). This repeats every year for the full lease term.
What is the London Trocadero case and why does it matter for insurance overcharges?
London Trocadero [2015] LLP v Picturehouse Cinemas Limited [2025] EWHC 1247 is a 2025 English High Court ruling that a landlord was not entitled to recover insurance rent representing commissions rebated to itself. The case establishes the principle that tenants should not bear insurance costs inflated by a self-directed rebate arrangement. While English authority is persuasive rather than binding in US courts, the underlying principle, that tenants pay actual insurance cost rather than inflated amounts including landlord profit, is well-established in US commercial lease practice.
How do I find out if my management fee exceeds the lease cap?
Locate the management fee provision in your lease. Note the cap percentage and the defined base for the calculation (often controllable expenses or total revenues). Take the authorized base amount from the reconciliation, multiply by the cap rate, and compare to the management fee that was actually billed. If the billed fee is higher, request the landlord's calculation backup showing how the fee was computed.
Can I recover overcharges from prior years on a modified gross lease?
Yes, within your lease's audit lookback window and the applicable state statute of limitations for written contracts. Texas, California, and most states provide 4 to 6 years for written contract claims. The clock typically starts at the reconciliation delivery date. Since software configuration errors tend to repeat every year once introduced, finding an overcharge in the current year almost always means the same error exists in prior years as well.
Related resources
- Modified Gross Lease Guide
- Expense Stops in Modified Gross Leases
- Excluded service charges in CAM statements
- Management Fee Overcharges
- Gross lease CAM charges
This article is for informational purposes only and does not constitute legal advice. Lease interpretation, operating expense obligations, and dispute rights vary by specific lease terms and jurisdiction. Consult a licensed commercial real estate attorney for advice specific to your situation.