Additional Insured Endorsement Explained: A Broker's Guide

An additional insured endorsement modifies a policy to extend coverage rights to a party beyond the named-insured. The additional insured can tender claims, demand defense, and seek indemnification - but only for liability arising from the named insured's operations or work. That scope limitation is where most disputes start.

Brokers who do not understand the endorsement forms, the difference from named insured status, and the primary-and-noncontributory requirement will eventually issue a certificate that creates E&O exposure. This guide covers the mechanics.

Key Takeaways

• Additional insured status is policy-level coverage by endorsement; it is not granted by the certificate.
• CG 20 10 covers ongoing operations; CG 20 37 covers completed operations. Most construction contracts require both.
• An additional insured on a commercial general liability policy is not automatically an additional insured on the commercial auto policy - that requires CA 20 48.
• Primary and non-contributory is a separate requirement on top of additional insured status.
• Blanket additional insured endorsements (CG 20 33, CG 20 38) cover all parties with a qualifying written contract - no scheduled list required.
• Named insureds have premium obligations and duty to cooperate; additional insureds do not.

What an Additional Insured Endorsement Does

The named-insured is the entity whose name appears on the policy declarations page. That entity purchased the policy, pays the premium, and has the full set of rights and obligations under the contract.

An additional insured is a third party added to the policy by endorsement. The endorsement extends specific coverage rights - typically defense costs and indemnification - to the additional insured for claims arising from the named insured's operations, products, or premises. The scope depends entirely on which endorsement form is attached.

The additional insured does not pay premium. They do not have a duty to cooperate in the same way. They cannot control policy terms or renewals. But they do have the right to tender a claim and demand that the named insured's carrier defend and indemnify them within the endorsement's scope.

This is the critical distinction brokers must explain to clients: a certificate of insurance does not make someone an additional insured. Only a policy endorsement does. A certificate that checks the additional insured box without a corresponding endorsement on the policy is a misrepresentation - and a direct source of E&O exposure.

The ISO Endorsement Forms That Control Everything

ISO publishes more than 30 additional insured endorsement forms. In practice, six forms handle nearly all commercial scenarios.

CG 20 10 - Owners, Lessees or Contractors (Ongoing Operations)

CG 20 10 is the standard additional insured endorsement for ongoing operations. It covers claims arising from the named insured's work while it is in progress. The 2013 edition (CG 20 10 04 13) added limiting language requiring that claims be "caused in whole or in part" by the named insured's acts or omissions. The 1993 edition (CG 20 10 10 93) used broader language and extended coverage to the additional insured's own negligence in some circumstances.

Many construction contracts specify "CG 20 10 10 93 or equivalent." Carriers no longer issue the 1993 edition. Agencies handling construction accounts need to understand that the 2013 form is narrower and may not satisfy that contract requirement.

CG 20 37 - Owners, Lessees or Contractors (Completed Operations)

CG 20 37 covers claims arising from the named insured's completed work - typically construction defect claims that surface years after project completion. This endorsement is essential for subcontractors, general contractors, and construction managers. Many claims in construction arise in the completed operations phase, not during active work.

CG 20 10 and CG 20 37 are routinely issued together to cover both phases. Contracts for construction work should specify both forms.

CG 20 33 and CG 20 38 - Blanket Additional Insured

These are the blanket endorsement forms. Rather than naming each additional insured individually, they automatically extend coverage to any person or organization with whom the named insured has a written contract requiring additional insured status.

CG 20 33 applies to owners, lessees, or contractors. CG 20 38 is the current ISO blanket form for ongoing operations. The blanket-additional-insured approach eliminates the administrative burden of scheduling each party - but requires a written contract signed before the loss.

CG 20 26 - Designated Person or Organization

CG 20 26 is a broader scheduled endorsement. It extends coverage to a designated additional insured for liability arising from the named insured's operations generally - not limited to operations specifically performed for the additional insured. This form appears in franchise agreements, vendor contracts, and large commercial lease structures.

CG 20 11 - Managers or Lessors of Premises

CG 20 11 is the landlord-tenant endorsement. It extends coverage to the landlord for liability arising from the tenant's use of the leased premises. Standard in commercial lease insurance requirements.

Named Insured vs Additional Insured: The Real Differences

Understanding what additional insured status does not include is as important as understanding what it does.

The most consequential difference in practice: coverage scope. A named insured has access to all coverages on the policy. An additional insured has rights only under the specific endorsement. A named insured's employee files a workers compensation claim - that is on the policy. An additional insured's employee files the same claim - that is not on the named insured's policy.

Notice of cancellation also differs. Named insureds receive statutory notice of cancellation. Additional insureds receive notice only if the endorsement specifically includes a notice obligation running to the additional insured. Many standard endorsements do not include this. Clients who need guaranteed notice - lenders, project owners, landlords - should require a separate endorsement providing that notice.

Additional Insured on a Commercial Auto Policy

CG 20 10 covers general liability. It does not extend additional insured status to the commercial auto policy. This is a frequent source of confusion.

To add an additional insured to a commercial auto policy, the carrier must attach form CA 20 48 (Designated Insured - Hired and Non-Owned Auto). CA 20 48 extends liability coverage under the commercial auto policy to the designated additional insured for claims arising from the use of the named insured's autos.

Some contracts require additional insured status on both general liability and commercial auto. Brokers need to process endorsements under both policies - CG 20 10 (and/or CG 20 37) for GL, and CA 20 48 for auto. A certificate showing additional insured on GL does not cover the auto exposure.

Carriers handle CA 20 48 differently. Some include it as a standard policy provision; others require a specific endorsement request. Confirm with the carrier before issuing the certificate.

Primary and Non-Contributory: What It Means and When It's Required

Primary-and-noncontributory is a separate requirement from additional insured status. It controls which policy responds first when both the named insured and the additional insured have coverage for a claim.

Standard additional insured endorsements make the named insured's policy share the loss with the additional insured's own GL policy - pro rata or by other allocation method. Primary and non-contributory language requires the named insured's policy to respond first, without seeking contribution from the additional insured's own coverage.

The endorsement that accomplishes this is typically CG 20 01 (Primary and Non-Contributory - Other Insurance Condition) or equivalent carrier-proprietary form. The ACORD 25 certificate includes a check box for "Primary, Non-Contributing." That box alone does not create the coverage - the policy endorsement must exist.

Contracts requiring primary and non-contributory coverage are common in:

• Construction master agreements
• Large commercial leases with national retail tenants
• Vendor agreements with Amazon, Walmart, and similar large enterprises
• Government contracts

When a contract requires primary and non-contributory, the broker must confirm CG 20 01 (or equivalent) is on the policy before issuing the certificate. Many carriers add this endorsement automatically when requested; others charge an additional premium of 3–10% of GL.

Blanket Additional Insured: How It Works in Practice

Blanket additional insured endorsements are the most operationally efficient approach for insureds with many additional insured requirements. A general contractor with 40 active projects and hundreds of subcontractor relationships cannot track 400 scheduled endorsements. A single blanket endorsement covers all of them - if the conditions are met.

The two conditions that matter most:

Written contract requirement. The blanket endorsement requires a written contract between the named insured and the additional insured that specifies the additional insured requirement. Verbal agreements, purchase orders, and handshake deals do not trigger blanket coverage. The contract must be in writing and must explicitly require additional insured status.

Pre-loss timing. The written contract must be signed and in place before the loss occurs. A subcontract executed after an incident does not retroactively activate blanket coverage for the party.

Blanket endorsements typically cost 3–7% of the GL premium. For contractors issuing 20+ certificates per year, the cost is often less than scheduling each party individually at $25–250 per endorsement.

The one workflow implication brokers miss: when a client has a blanket endorsement, verifying coverage for a specific certificate request means confirming (a) the written contract exists, (b) the contract requires additional insured status, and (c) the contract was in place before any relevant loss date. This is an agency-side workflow question, not just a certificate question.

Common Endorsement Errors and Their Consequences

Issuing CG 20 10 without CG 20 37 on a construction account. The additional insured is covered during active work but not for completed operations claims - which is where many construction defect claims arise. The error surfaces years later.

Using a blanket endorsement when the written contract does not specify additional insured status. The blanket endorsement does not activate. The additional insured has no coverage. The certificate misrepresents the coverage.

Missing CA 20 48 on a contract requiring auto additional insured. The GL certificate looks correct. The auto exposure is uncovered. A vehicle accident on the jobsite creates uninsured exposure for the project owner.

Failing to add CG 20 01 when the contract requires primary and non-contributory. The additional insured status exists but the coverage is not primary. The additional insured's carrier seeks contribution from the named insured's carrier. Contract dispute follows.

For more on certificate issuance and endorsement management, see our additional insured tracking guide and COI workflow for construction accounts.

Frequently Asked Questions

What is an additional insured endorsement on a commercial policy?

An additional insured endorsement modifies a commercial general liability policy to extend coverage rights to a party beyond the named insured. The additional insured receives the right to tender claims and demand defense and indemnification for liability arising from the named insured's operations or work - within the scope defined by the specific endorsement form attached to the policy. The most common forms are CG 20 10 (ongoing operations) and CG 20 37 (completed operations).

What is an additional insured on a commercial auto policy?

An additional insured on a commercial auto policy requires a separate endorsement - CA 20 48 (Designated Insured - Hired and Non-Owned Auto). The standard GL additional insured endorsements (CG 20 10, CG 20 37) apply only to general liability coverage and do not extend to the commercial auto policy. Contracts requiring additional insured on both lines need both endorsements processed separately.

How is an additional insured different from a named insured?

A named insured has purchased the policy, pays the premium, and has full policy rights and obligations - including the duty to cooperate, access to all coverages, and control over policy terms. An additional insured receives coverage rights only under the specific endorsement, has no premium obligation, and cannot control the policy. Named insureds receive statutory notice of cancellation; additional insureds receive notice only if the endorsement specifically provides for it.

Does a certificate of insurance make someone an additional insured?

No. A certificate of insurance is an informational document only. ACORD 25 includes a disclaimer stating that the certificate does not confer rights upon the certificate holder and does not modify the policy. Only a policy endorsement creates additional insured status. A certificate that represents additional insured status when no corresponding endorsement exists on the policy is a misrepresentation - and a source of direct E&O exposure for the issuing agency.

What does primary and non-contributory mean for additional insureds?

Primary and non-contributory means the named insured's policy responds first to a claim involving the additional insured, without seeking contribution from the additional insured's own insurance. Standard additional insured endorsements allow the named insured's carrier to seek contribution from the additional insured's carrier - sharing the loss. Primary and non-contributory eliminates that contribution right. This requires a separate endorsement (typically CG 20 01) and commonly costs 3–10% additional GL premium. It is required by many construction contracts, large commercial leases, and enterprise vendor agreements.

When should you use a blanket additional insured endorsement?

Use a blanket additional insured endorsement when the insured has ongoing additional insured requirements across multiple contracts, projects, or vendors - and when tracking individual scheduled endorsements would be operationally burdensome. A blanket endorsement covers all parties with a qualifying written contract requiring additional insured status. It is cost-effective (3–7% of GL premium vs $25–250 per scheduled party) and reduces the risk of a specific party being missed. The written contract must pre-date any loss for coverage to apply.

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

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