Additional Insured: Definition and How It Works

An additional insured is a person, organization, or entity that is added to an insurance policy — typically a Commercial General Liability (CGL) policy — by endorsement, granting them defined coverage rights under someone else's policy. The additional insured is not the policy owner (the named insured) but is afforded protection for liability arising out of the named insured's operations, work, or products. Additional insured status is one of the most requested and frequently misunderstood elements of commercial insurance, and improper handling of additional insured endorsements is a leading source of broker Errors & Omissions (E&O) claims.

Why Additional Insured Status Is Requested

Additional insured requests arise from contractual risk transfer. In construction, real estate, and service contracts, one party (a general contractor, landlord, client, or government entity) typically requires the other (a subcontractor, tenant, vendor, or service provider) to add them as an additional insured on the vendor's CGL policy. The purpose is to extend liability protection to the party who directed or benefited from the work, and to ensure that the primary source of recovery for a covered claim runs through the contractor's policy rather than the requiring party's own insurance.

Common scenarios where additional insured status is required:

• General contractor / subcontractor: A GC requires all subs to add the GC (and sometimes the project owner) as an additional insured on their GL policy
• Landlord / tenant: A commercial landlord requires tenants to add the landlord to their CGL policy
• Client / vendor: A corporate client requires service vendors to provide AI status as a condition of the contract
• Lender / borrower: A lender requires a property owner's liability policy to include the lender as an AI
• Government contracts: Federal, state, and municipal agencies frequently require AI status

How Additional Insured Endorsements Work

The additional insured's coverage is added by endorsement — a policy modification attached to the named insured's policy. The most common ISO endorsements for CGL policies are:

• CG 20 10 (Additional Insured — Owners, Lessees, or Contractors — Scheduled): Covers the AI for liability arising out of ongoing operations of the named insured
• CG 20 37 (Additional Insured — Owners, Lessees, or Contractors — Completed Operations): Covers the AI for liability arising out of completed work
• CG 20 26 (Additional Insured — Designated Person or Organization): A broader form that can cover various relationships

Many contracts require both CG 20 10 and CG 20 37 to be attached, covering both the construction period and the post-completion liability period. Failing to attach the correct form is a common broker E&O exposure — a construction defect claim surfaces after project completion, and the AI only has CG 20 10 (ongoing operations only), leaving a gap.

Scope of Additional Insured Coverage

An additional insured's coverage under the endorsement is not coextensive with the named insured's coverage. Key limitations:

• Arising out of: Most AI endorsements cover the AI only for liability arising out of the named insured's work or operations — not the AI's own independent negligence. If the AI is solely at fault, coverage may not attach.
• Primary and non-contributory: Contracts often require that the named insured's policy be primary and non-contributory to the AI's own insurance. The AI endorsement must expressly provide this, or the two policies may share the loss. Without a "primary and non-contributory" provision in the endorsement, the AI's own insurer may seek contribution.
• Policy limits: The AI accesses the named insured's policy limits. If the named insured has already depleted limits through prior claims, the AI has reduced protection.
• Notice requirements: Additional insureds may have independent notice obligations under the policy; failure to provide timely notice can jeopardize coverage.

Certificate of Insurance and Additional Insured Documentation

The primary document evidencing additional insured status is the ACORD 25 Certificate of Insurance. A certificate of insurance (COI) lists the additional insureds and summarizes coverage, but it is important to understand: a COI is an evidence of insurance document, not a contract. The COI cannot expand coverage beyond what the actual endorsement provides. Contractual language that requires a COI with certain provisions does not guarantee that the underlying endorsement matches those provisions.

Brokers who issue certificates that overstate coverage — or fail to verify that the required endorsements are actually attached — face significant E&O exposure. For the full obligations and E&O risks associated with certificate issuance, see Certificate of Insurance Guide.

Additional Insured vs Named Insured vs Loss Payee

Related Terms

• Errors and Omissions Insurance — AI endorsement errors are one of the leading causes of broker E&O claims; proper endorsement matching is a critical professional responsibility
• Occurrence Policy — additional insured status on an occurrence-form CGL policy provides permanent protection for covered incidents that occurred during the policy period, even after the policy has expired
• Subrogation — insurers may waive subrogation rights against additional insureds; contracts often require a waiver of subrogation endorsement alongside the AI endorsement

How Brokers Use Additional Insured Endorsements in Practice

Reviewing contracts for insurance requirements — specifically the required AI endorsements, limits, and primary/non-contributory language — is a core service that commercial brokers provide to clients. When onboarding a new commercial client, brokers should review all active contracts for insurance requirements, verify that the current policy attachments satisfy those requirements, and flag gaps. Failure to identify a missing AI endorsement before a loss is a significant E&O exposure. For the broader coverage design context, see CGL vs Professional Liability.