Understanding Additional Insured Coverage Limitations for Insurance Brokers

Additional insured coverage limitations are the most misunderstood aspect of commercial lines certificate management. IIABA 2025 reports that AI-related coverage misunderstandings are the leading source of COI-related E&O claims for agents and brokers in commercial lines.

The misunderstanding starts with a simple assumption: a certificate holder who sees "additional insured" on a COI believes they have the same protection as the named insured. They do not. AI coverage is narrower, conditional, and tied to the named insured's operations in ways that most certificate holders never learn until after a claim is denied.

This post gives you a checklist of the specific additional insured coverage limitations you must communicate to clients, and the documentation practices that protect your agency when coverage disputes arise.

Key Takeaways

• ISO CG 20 10 (ongoing operations) and ISO CG 20 37 (completed operations) are different endorsement forms. Many contracts require both. Verifying which form is on the policy is a mandatory step before issuing a certificate (ISO 2024).
• AI coverage under a standard GL policy does not include workers' compensation. A certificate holder who wants WC protection needs a separate contractual agreement with the named insured, not an AI endorsement.
• Additional insureds do not receive a separate policy aggregate. If the named insured exhausts their aggregate on other claims, the AI has no remaining coverage under that policy for the same period.
• AI status expires with the policy. If the named insured's policy cancels and no new endorsement is issued on the renewal, the certificate holder is uninsured under the new policy period regardless of any prior certificate.
• ISO CG 20 10 covers only vicarious liability arising from the named insured's acts or omissions. If the certificate holder is solely at fault, the named insured's policy does not respond (ISO 2024).
• Documenting the endorsement form, coverage trigger, and AI limitations in writing at the time of certificate issuance is the single most effective E&O protection available to agents in commercial lines servicing.

The Core Misunderstanding

Most certificate holders think "additional insured" means "covered like the named insured." It does not.

The named insured has a direct contractual relationship with the insurer. They pay premiums. The policy is built for their operations. When a claim arises, the policy responds to the named insured's losses subject to its terms.

An additional insured has no direct relationship with the insurer. Their coverage is derivative. It exists only through an endorsement on the named insured's policy, and that endorsement defines the scope of AI coverage precisely and narrowly. The AI gets coverage only for the specific types of liability the endorsement addresses, and nothing more.

IIABA 2025 identifies AI coverage misunderstanding as the most common COI-related E&O trigger in commercial lines. The agent issues a certificate, the certificate holder assumes they are fully covered, a claim arises, and coverage is denied or disputed. The agency then faces an E&O claim from the certificate holder.

The solution is proactive disclosure. Every certificate with an AI notation should be accompanied by a written explanation of what AI status does and does not provide.

The 7 Additional Insured Coverage Limitations

Limitation 1: AI Coverage Covers Only Vicarious Liability

ISO CG 20 10 is the standard ongoing operations AI endorsement. Its coverage is specific: it covers the liability of the additional insured arising from the named insured's acts or omissions. That is vicarious liability, not direct liability.

If the additional insured is solely at fault for an incident, ISO CG 20 10 does not respond. The named insured's policy is not designed to protect the AI from their own negligence. It covers the AI only when the named insured caused or contributed to the loss.

This is a significant limitation that most certificate holders do not understand. A general contractor added as AI to a subcontractor's GL policy has no coverage under that policy if the GC's own workers caused the injury without any contribution from the subcontractor. The AI needs their own GL policy for that exposure.

Tell your clients: AI status protects you when the named insured's operations cause or contribute to a loss. It does not replace your own liability coverage.

Limitation 2: No Workers' Compensation Extension

AI status on a GL policy does not extend to the named insured's workers' compensation policy. Workers' compensation is a statutory benefit, not a liability endorsement. WC policies do not have AI endorsements.

A certificate holder who wants protection from WC claims by the named insured's employees needs a contractual hold-harmless agreement and their own liability coverage, not an AI endorsement. If a named insured's employee is injured at the certificate holder's job site and sues the certificate holder, the named insured's WC policy will pay the employee's WC benefits. It will not defend or indemnify the certificate holder in that lawsuit.

This distinction matters particularly in construction. General contractors routinely require AI status from subcontractors. They often assume that AI status on the GL policy means they are protected from all claims by the subcontractor's workers. It does not.

Limitation 3: AI Status Expires with the Policy

When a named insured's policy expires, cancels, or non-renews, any AI endorsements on that policy expire with it. If the named insured obtains a renewal policy and no new AI endorsement is issued naming the certificate holder, the certificate holder has zero coverage under the new policy period.

This is a gap that frequently goes undetected. The certificate holder has a COI from the prior policy year. They assume coverage continues. The named insured has a new policy. No one issues an updated AI endorsement. No one sends a new certificate. A claim arises under the new policy period, and the AI has no endorsement.

Agents should build a renewal review into their certificate management process. At every renewal, verify that all standing AI requirements have been reissued on the new policy. Document this verification.

Limitation 4: Ongoing Operations vs. Completed Operations

Two distinct ISO endorsement forms address AI coverage for construction and contractor work:

• ISO CG 20 10: covers ongoing operations. This means incidents that occur while the named insured is actively working on the project.
• ISO CG 20 37: covers completed operations. This means incidents that occur after the project is finished.

Many construction contracts require both forms. A subcontractor might provide CG 20 10 (ongoing) but not CG 20 37 (completed operations). The general contractor then has no AI coverage for a claim that arises after the project is complete, which is exactly when construction defect claims typically surface.

ISO 2024 data shows that completed operations claims are the single largest category of construction defect liability claims by dollar value. An AI without CG 20 37 coverage has no protection for this exposure.

Before issuing a certificate, verify which ISO AI endorsement form is on the policy. If the contract requires both and only one is present, that is a coverage gap that must be resolved with the carrier before the certificate goes out.

Limitation 5: Professional Liability Is Not Included

GL AI endorsements cover general liability. They do not cover professional liability, design errors, engineering negligence, or professional services claims.

A general contractor added as AI to a design-build subcontractor's GL policy has no coverage under that policy for a claim alleging design error or professional negligence. GL policies contain professional services exclusions. Those exclusions apply to both the named insured and any additional insureds.

If a certificate holder needs protection from professional liability claims arising from the named insured's professional services, they need to require the named insured to carry professional liability (errors and omissions) coverage. That coverage does not have AI endorsements in the traditional sense. The protection must come through contract indemnification, not a GL AI endorsement.

Tell clients: AI status on a GL policy protects you from general liability claims. It does not protect you from professional liability claims.

Limitation 6: Shared Aggregate Limit

The additional insured does not get a separate policy aggregate. The named insured's aggregate limit is shared across all claims under the policy, including claims by the AI.

If the named insured has a $2,000,000 aggregate and has already paid $1,800,000 in claims during the policy period, the remaining aggregate available to the additional insured for their claim is $200,000. The COI the AI received at the start of the policy period showed $2,000,000. That number is no longer accurate.

This is one of the reasons that sophisticated certificate holders in high-value contracts request updated certificates mid-year and ask carriers to confirm aggregate erosion. For most standard commercial relationships this is not practical, but in construction contracts over $1 million it is worth requiring.

Agents must disclose this limitation to clients who are adding AI endorsements: the aggregate the AI sees on their certificate reflects the policy maximum, not the remaining available limit.

Limitation 7: Endorsement Form vs. Description of Operations Language

The Description of Operations field on an ACORD 25 may say "additional insured as required by written contract" or similar language. But the actual coverage the AI receives depends on which endorsement form is physically on the policy, not what the Description of Operations says.

If the contract requires a blanket AI endorsement but the policy has a scheduled endorsement (CG 20 10 with specific names), there may be a mismatch between what the contract requires and what the policy provides. If the contract requires primary and noncontributory language but the AI endorsement does not include it, the Description of Operations notation does not create that obligation on the insurer.

ACORD 2025 explicitly notes that Description of Operations language does not modify policy terms. The endorsement form controls. Verify the endorsement form before noting any coverage representation in the Description of Operations.

AI Limitations Checklist: Quick Reference

What Agents Must Document

When a client requests AI status for a certificate holder, the file documentation should include:

1. The specific AI endorsement form on the policy: CG 20 10, CG 20 37, blanket AI endorsement, or other. This is not optional. The form determines the scope of coverage.
2. The coverage trigger: ongoing operations, completed operations, or both. For construction accounts, verify both are required and both are on the policy.
3. Confirmation from the carrier or policy review: do not rely on what the prior certificate said or what the named insured tells you. Pull the endorsement schedule.
4. Written disclosure sent to the client: confirm in writing the AI endorsement was added, which form was used, and the limitations of AI status. Email is sufficient. Keep the record.
5. Date of verification: document when you confirmed the endorsement, not just that you did.

This documentation does not take more than five minutes per certificate. It creates a clear record that the agency performed its duty and disclosed the limitations of the coverage it facilitated.

The E&O Risk of Undisclosed AI Limitations

IIABA 2025 data shows that AI-related coverage disputes are the most common source of COI-related E&O claims in commercial lines. The claim pattern is predictable:

• Agent issues a certificate noting AI status
• Certificate holder assumes full coverage
• Named insured's policy covers a narrow scope of AI liability
• A claim arises outside that scope (sole fault, professional liability, completed operations not endorsed, aggregate exhaustion)
• Coverage is denied
• Certificate holder sues the agent for misrepresentation or failure to disclose

The agent's defense is documentation. If the agency can show that it disclosed the limitations of AI coverage in writing at the time of issuance, the E&O claim is significantly harder to sustain. If there is no disclosure and no documentation, the agency has an uphill defense.

This is not a difficult problem to solve. It requires a disclosure template, a documentation step in the certificate issuance workflow, and consistent execution.

Frequently Asked Questions

Does additional insured status give a certificate holder the same coverage as the named insured?

No. Named insured coverage is broad and direct. AI coverage is derivative and limited. Under ISO CG 20 10, the AI only has coverage for liability arising from the named insured's acts or omissions. The AI has no coverage under the policy for their own direct negligence, professional liability claims, or incidents outside the scope of the named insured's operations. The certificate holder always needs their own separate liability coverage in addition to any AI status they hold.

What is the difference between ISO CG 20 10 and CG 20 37 for additional insureds?

ISO CG 20 10 covers liability arising from the named insured's ongoing operations: work that is actively in progress during the policy period. ISO CG 20 37 covers completed operations: liability arising after the named insured's work on a project is finished. Construction contracts typically require both. An AI who only has CG 20 10 has no coverage for post-project claims, which is precisely when construction defect claims arise. Agents must verify which form or forms are on the policy before issuing a certificate in any construction context (ISO 2024).

Does additional insured status include workers' compensation coverage?

No. Workers' compensation is a statutory benefit program. GL policies do not extend AI status to WC coverage. The named insured's WC policy will pay benefits to injured employees regardless of where the injury occurs. But it does not defend or indemnify the additional insured if that AI is sued in connection with the injury. Certificate holders who want protection from claims by the named insured's employees need a contractual indemnification agreement and their own GL coverage.

What happens to additional insured coverage when the named insured's policy cancels?

It terminates. AI endorsements are part of the named insured's policy. When the policy cancels or non-renews, all endorsements end with it. If the named insured obtains a new policy and no new AI endorsement is issued naming the certificate holder, the certificate holder has no coverage under the new policy. Agents must verify at every renewal that all standing AI requirements are re-endorsed on the new policy.

Do additional insureds get their own policy aggregate limit?

No. The additional insured shares the named insured's aggregate limit. If the named insured has used a significant portion of their aggregate on other claims during the policy period, the AI's effective available coverage is reduced by the same amount. The aggregate shown on the original COI reflects the policy maximum, not the current available limit. For high-value contracts, consider requiring the named insured to carry higher aggregate limits or umbrella coverage to protect against aggregate erosion.

What should a broker document when adding an additional insured to a policy?

Document four things: the specific AI endorsement form on the policy, the coverage trigger (ongoing, completed, or both), the date you confirmed the endorsement with the carrier or endorsement schedule, and any written disclosure sent to the client explaining AI coverage limitations. This documentation creates the record that the agency performed its obligations. It is the primary defense in an E&O claim and takes fewer than five minutes per certificate transaction.

BrokerageAudit tracks which AI endorsement forms are on each policy and verifies the coverage trigger so your certificates reflect actual policy terms. See how it works →

Written by Javier Sanz, Founder of BrokerageAudit. Last updated April 2026.