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Additional insured endorsements explained

What CG 20 10, CG 20 37, CG 20 26 and CG 20 38 do, how the 04 13 wording limits additional insured coverage, and why a certificate is not the endorsement.

4BusinessInsurance · Published October 10, 2026

An additional insured endorsement adds another person or business to your commercial general liability (CGL) policy as an insured, but only for liability that your work or premises creates for them. It does not make them a named insured, give them their own limits or cover their own independent negligence under the current ISO wording. The form number and edition on the endorsement decide the scope, and a certificate of insurance with the "additional insured" box checked is not the endorsement.

What additional insured status gives and what it does not

On the standard CGL form, Section II defines who is an insured. An additional insured endorsement amends that section so a party named in the schedule (or described in a blanket wording) is treated as an insured for a defined slice of liability. That brings the policy's defense obligation along; see the insurer's duty to defend: what triggers it and when it ends. It also means the additional insured shares the limits with you. If the policy limit is $1 million per occurrence, you and the additional insured together get $1 million, and a claim against one erodes what is left for the other.

Role	What the party gets	Typical example
Named insured	Full insured status, premium obligations, right to cancel and change the policy	The subcontractor that bought the policy
Additional insured	Insured status for liability tied to the named insured's work, premises or operations, as the endorsement defines	The general contractor, the project owner, a landlord
Certificate holder	Information only; no rights under the policy	A client that asked for a certificate
Loss payee or mortgagee	A payment interest in a property loss, not liability coverage	A lender with an interest in your building

The main ISO endorsements

The ISO forms used most often are below. Titles and scope are drawn from the endorsements themselves and from the County of Sonoma's public contract insurance reference guide.

Form	Title	What it is for
`CG 20 10`	Additional Insured, Owners, Lessees or Contractors, Scheduled Person or Organization	Ongoing operations performed for the scheduled party at the scheduled location
`CG 20 37`	Additional Insured, Owners, Lessees or Contractors, Completed Operations	Injury or damage that occurs after the work is finished, from your work included in the products-completed operations hazard
`CG 20 26`	Additional Insured, Designated Person or Organization	A general-purpose form for parties that do not fit a construction relationship; covers operations and premises, not completed work
`CG 20 38`	Additional Insured, Owners, Lessees or Contractors, Automatic Status for Other Parties When Required in Written Construction Agreement	Blanket status for parties you do not contract with directly, such as a project owner above a general contractor, when a written construction agreement requires it
`CG 20 11`	Additional Insured, Managers or Lessors of Premises	A landlord or property manager of premises you occupy

The completed-operations gap is the one that catches people. CG 20 10 covers ongoing work. Once the job is done or the work has been put to its intended use, it stops applying, so a contract that wants protection for years afterward needs CG 20 37 or an equivalent. See products and completed operations coverage.

Reading CG 20 10 04 13

A public sample of the 04 13 edition posted by the City of Yorba Linda shows what the wording does, in five moves:

The grant. The scheduled party is an insured only for bodily injury, property damage or personal and advertising injury "caused, in whole or in part, by" your acts or omissions, or those of people acting on your behalf, in your ongoing operations for that party at the scheduled location. If you had nothing to do with the injury, there is no coverage for the additional insured, and the form does not respond to the additional insured's sole negligence.
The law carve-out. Coverage applies only to the extent permitted by law. In states with anti-indemnity statutes, that phrase narrows the grant. See below.
The contract ceiling. If a contract requires the additional insured coverage, it will not be broader than the contract requires.
The completion exclusion. The additional insured has no coverage for injury or damage after all work on the project has been completed, or after the part of your work involved has been put to its intended use by someone other than another contractor on the same project.
The limit clause. When a contract requires the coverage, the most the insurer pays for the additional insured is the lesser of the amount the contract requires or the limit shown in the declarations. The endorsement does not increase the limits.

ISO has narrowed these forms over the years, so older editions such as the 11 85 version were broader. The edition date is printed in the form number. ISO also announced a revised CGL multistate forms package for policies written on or after October 1, 2026, according to a July 2026 circular tracker, so confirm which edition is attached to the policy you are reviewing. Carriers also use their own proprietary endorsements, which may be narrower or broader than ISO's and have to be read one at a time.

Scheduled versus blanket

A scheduled endorsement lists each additional insured by name. A blanket endorsement says that anyone you are required by written contract to add is an additional insured, and no name appears on the form. Blanket wording is convenient when you sign many contracts, but it has conditions: the contract must require the status, the scope matches what the contract asks for, and carrier wording varies on whether the contract must have been signed before the loss. Where an endorsement lists names, spell them exactly. Public owners' insurance guides warn that an entity not listed precisely is not covered, and a parent, a lender or a property manager that the contract mentions but the schedule omits can end up with nothing.

Where additional insured coverage falls short

Completed operations. Discussed above. Renewals matter, too: a form that limits completed-operations coverage to work done during the current policy period leaves a gap when the policy renews.
Shared and eroding limits. The additional insured draws on your limits. Your own claims, or those of other additional insureds, may have used them already.
Excess and umbrella. A contract that wants $5 million of protection needs an umbrella that extends insured status to the additional insured. See commercial umbrella insurance.
Anti-indemnity laws. Texas Insurance Code section 151.104 makes additional insured requirements in construction contracts void to the extent they would provide coverage the chapter prohibits as indemnity, and section 151.151 says the chapter cannot be waived by contract. See contractual liability coverage and insured contracts and Texas. Other states have statutes of their own, so check the state that governs the contract.
Professional services. Professional services exclusions can remove design and engineering exposures. An additional insured on your CGL does not fill that gap.
Order of payment. Additional insured status does not say whose policy pays first. That takes primary and noncontributory wording; see primary and noncontributory wording in contracts.
Waiver of subrogation. Also a separate endorsement. See waiver of subrogation: what it is and when contracts require it.

A worked example (hypothetical)

Say an HVAC subcontractor in Texas installs a rooftop unit for a general contractor. The subcontract requires CG 20 10 and CG 20 37 with completed operations maintained for three years after completion. The subcontractor's broker issues a certificate showing the general contractor as additional insured and attaches only CG 20 10.

Eighteen months after the unit is placed in service, a refrigerant line fails and floods a tenant's inventory. The tenant sues the general contractor, who tenders the claim to the subcontractor's insurer as an additional insured. The claim is for property damage that occurred after the work was complete, which the CG 20 10 exclusion removes. Without CG 20 37, the general contractor has no additional insured coverage, and its claim against the subcontractor becomes a breach-of-contract dispute over the missing endorsement. That is a loss the subcontractor's CGL generally does not cover, since failing to buy required insurance is a breach of contract rather than covered liability. If CG 20 37 had been attached, the general contractor would be an insured for property damage caused in whole or in part by the subcontractor's work, subject to the policy's other terms. The outcome of a real claim depends on the exact forms and facts, so treat this as a pattern.

How to request and verify the endorsement

Give your broker the exact insurance clause from the contract, not a summary.
Ask for the specific form numbers and edition dates, or an equivalent that your counsel or the other party accepts.
Make sure names, locations and project descriptions are exact.
Ask for ongoing and completed operations coverage, and for how long completed operations will be maintained.
Get copies of the endorsements, not only the certificate. The certificate form itself says a statement on it does not confer rights in place of an endorsement; see certificates of insurance: what they prove and what they do not.
Match what the contract demands to what the policy provides. The contract insurance requirements checker helps, and how to review the insurance requirements in a contract walks through the review.
If you are the additional insured and a claim arrives, tender it promptly to the other party's insurer and your own. See tendering a claim to another party's insurer.

Key takeaways

An additional insured endorsement gives limited insured status for liability tied to your work, premises or operations, using your limits.
CG 20 10 covers ongoing operations; CG 20 37 is the usual answer for completed operations. Contracts often need both.
The 04 13 wording requires that your acts or omissions caused the injury at least in part, and limits coverage to what the contract requires and the law allows.
Blanket and proprietary forms differ from ISO's, so read the actual endorsement and its edition date.
A certificate marked "additional insured" proves nothing about the endorsement. Ask for the form.

Terms used in this guide

Additional insured A person or business added by endorsement to someone else's liability policy so it can claim directly for suits tied to the policyholder's work or premises. Endorsement A written amendment to an insurance policy that adds, removes or changes coverage, limits or conditions, and controls over the base form where they conflict. Named insured The person or entity identified as the insured in the policy's declarations, which holds the coverage and its duties; others qualify only if the policy says so. Products-completed operations aggregate The most a general liability policy pays per policy period for injury or damage in the products-completed operations hazard, apart from the general aggregate. Completed operations Liability coverage for injury or damage that occurs after a contractor or service provider finishes a job and leaves, arising out of the finished work. Duty to defend A liability insurer's obligation to pay for your defense of a lawsuit that could potentially fall within coverage, which is broader than its duty to pay.

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