The additional insured endorsement provides coverage to an associate of your business (landlord, general contractor, project owner) by giving them insured status on your general liability policy. What type of coverage is provided depends solely upon the form number. One family will provide coverage for your ongoing operations while the other will provide coverage for your completed operations. No current edition increases your limit of insurance nor provides coverage when the sole negligent party is the additional insured.
The split that matters most is CG 20 10 against CG 20 37. The first responds while your crews are still on the jobsite. The second responds after the work is done, and construction contracts commonly demand both. If you sign construction contracts or commercial leases, you have almost certainly been asked for one. Here is what the request actually means, grounded in the ISO forms most insurers use.
Additional Insured Endorsement
A General Liability Policy Additional Insured Endorsement adds an individual or company (i.e. a landlord or a general contractor) to your general liability insurance coverage so that they are also insured with respect to claims caused in whole or in part by your work or your acts and omissions. The additional insured will not be covered for losses resulting from their own sole negligence, and adding the other party does not increase the policy's limits.
What is an additional insured?
The CGL policy automatically insures certain people: the named insured, and automatic insureds like employees acting within their duties (see what general liability insurance covers for the full list). An additional insured is a third category, a person or organization deliberately granted insured status by endorsement because of a business relationship. Three relationships account for nearly every request. First, you perform work for the party, such as a project owner or a general contractor hiring you as a subcontractor. Second, the party owns premises or equipment you use or lease, which is the landlord and equipment lessor case. Third, the party holds a financial stake in your operation, such as a lender. The first two groups generate almost all the volume, and construction generates almost all the disputes.
Businesses demand the status because the contract promise alone can collapse. Construction agreements and leases pair a hold harmless clause, your written promise to absorb the other party's losses, with an additional insured requirement, because that promise may not survive on its own. Most states restrict indemnity by statute, and California Civil Code Section 2782 voids construction contract clauses that try to indemnify a party for its own sole negligence.[1] When a court strikes the indemnity clause, the endorsement still stands. Insured status also carries mechanical advantages no contract clause can deliver. The additional insured's defense is paid as a supplementary payment outside the limit, and the named insured's carrier will not subrogate against a fellow insured on the same policy.
What is the difference between CG 20 10 and CG 20 37?
The two most common types of endorsements divide a construction project in half at the point of completion:
| Feature | CG 20 10 12 19 | CG 20 37 12 19 |
|---|---|---|
| Full title | Additional Insured: Owners, Lessees Or Contractors, Scheduled Person Or Organization | Additional Insured: Owners, Lessees Or Contractors, Completed Operations |
| Covers | Injury or damage caused in whole or in part by your acts or omissions during ongoing operations for the additional insured | Injury or damage caused in whole or in part by your work, within the products-completed operations hazard |
| Coverage lines | Bodily injury, property damage, and personal and advertising injury | Bodily injury and property damage |
| Written contract required by the form? | No, the party is scheduled | No, the party is scheduled |
| Completed Operations? | Excluded: The insurance ends once the work is completed or put to its intended use. | That is the point |
CG 20 10 shuts off when the project is finished, and construction claims routinely surface after completion. That is why contracts commonly require both endorsements, often with the CG 20 37 maintained for two or three years after completion, or for the statute of repose period. That post-completion exposure is the same one that makes builders risk and completed-operations planning so important for contractors.
What about automatic additional insured status?
Scheduling every party on every project gets unwieldy, so ISO publishes automatic-status versions. The market calls them blanket additional insured endorsements, and they grant insured status whenever a written contract requires it. CG 20 33 covers ongoing operations for parties you contract with directly. CG 20 38 extends to other parties, like a project owner, named in your customer's contract even if they never signed anything with you. CG 20 39 and CG 20 40 are the completed-operations counterparts.
"Blanket" endorsement seems to provide coverage for all parties involved with the project, and that is exactly how most certificate reviewers treat it. It does not. These endorsements respond only when a written contract requiring additional insured status already exists, and that contract has to be signed before the bodily injury or property damage occurs. In actuality this means you will need to get the signature prior to the time that the work that causes the loss starts. Do not wait until after the accident to obtain the signature. The above types of situations (Unsigned Contracts, Contracts Signed Mid-Project, Master Agreements that lapsed before the Work Order) are the classic blanket-form coverage fights.
The dispute regarding which of them signed to be included in whose insurance policy has now made its way to New York's highest Court. In Gilbane Bldg. Co. v. St. Paul Fire & Marine Ins. Co. (2018) a construction manager for the state forensic laboratory project claimed they were entitled to additional insured status under the General Contractor's Policy because the Owner's Contract required it. The Endorsement extended coverage to organizations "with whom you have agreed to add as an additional insured by written contract," and Gilbane had entered into no such written Agreement with the General Contractor. Coverage failed due to the use of one preposition.[2] That gap is exactly what CG 20 38 was built to close.
What does additional insured status not do?
ISO tightened these forms substantially in 2004 and after, and the limitations matter on both sides:
- No sole-negligence coverage: the 2004 revision changed "arising out of" to "caused by," requiring a causal connection to the named insured's acts, omissions, or work.
- No increase in limits: every insured, named and additional, shares the same limits, with no priority for anyone.
- No coverage beyond the contract: Recent editions have been drafted to limit coverage to the lower of the amount the contract requires or the named insured's available limits.
- No control of the defense: The Named Insured's Carrier will investigate, defend and settle. The Additional Insured has no authority to make these decisions and the possibility of defending both sides can lead to some real potential conflict as each party's best defense may be blaming the other.
If you are protected only as an additional insured then you are also subject to that policy's exclusions as well as the potential for its cancellation or nonrenewal and/or have its aggregate limits silently diminished through other claims without your knowledge. Your additional insured status enhances your own CGL coverage but never replaces it.
What does "primary and noncontributory" mean?
Usually, contracts also call for secondary stipulation that the named insured's coverage is to be primary and noncontributory. In other words, the named insured's insurance policy will pay out prior to the additional insured's insurance policy paying out on a claim, as well as requiring no contribution from the insurer of the additional insured. If this were not included in a contract, The CGL's Other Insurance Condition can cause both primary policies (the Named Insured's and Additional Insured) to contribute toward a claim, thus reducing what the Named Insured was expected to cover with their own policy completely.
The solution is through use of a "Primary and NonContributory: Other Insurance Condition" endorsement (CG 20 01 12 19). This amendment changes the wording of the "Other Insurance Condition" so the Named Insured's policy pays first and will not seek contribution from the Additional Insured's insurance (subject to a written contract requiring such).
When a request arrives, follow the process of working through all of the exhibits related to insurance in order. Determine which entities will have to be added (and which form number(s) or edition date(s)) referenced by name. Next identify each entity relationship with a corresponding form. Ensure that both primary and noncontributory language is actually attached as opposed to being merely implied. Finally, provide documentation using a certificate of insurance listing the endorsements. This will demonstrate that there is actual coverage under an endorsement when a certificate alone confers no coverage. If a contract calls for something outside of standard practice, prior to signing it is best to first speak with your broker regarding any discontinued editions such as CG 20 10 11 85, etc., or wording your carrier has not filed. Signing agreements requiring insurance terms that your policy cannot deliver can result in breaches of contracts being exposed during subsequent claims against those policies.
Frequently asked questions
What's the difference between an additional insured and a certificate holder?
A certificate holder simply obtains an insurance certificate as proof that there is coverage. However, this does not grant the certificate holder rights to the policy. The additional-insured person is added to the policy via endorsement and therefore has insured status (including a right to defense) and can make a claim against the policy limits if a covered loss occurs.
What is the difference between an additional interest and an additional insured?
An Additional Interest (sometimes called an "Interested Party") has NO Coverage Rights - only notification rights (i.e., notice of cancellation or material changes) related to the Policy, whereas an Additional Insured is Endorsed onto the Policy itself and receives Defense and Indemnification for Covered Claims. For example, a Landlord would typically be considered an "Additional Interest" on a Renter's Policy if they are listed as such by their Tenant. On the other hand, a General Contractor would be considered an "Additional Insured" if it is endorsed into a subcontractor's CGL Policy.
Does an additional insured endorsement cover the additional insured's own negligence?
Partly. The current ISO versions of the form cover additional-insured persons for losses resulting from injuries or damages to people or property caused in whole or in part by the acts or omissions of the Named Insured, which includes joint negligence of both parties. However, these forms do NOT provide coverage where all negligence was attributed solely to the additional-insured party.
Do I need both CG 20 10 and CG 20 37?
Usually yes on construction projects if the contract requires completed operations coverage. CG 20 10 ends at completion and CG 20 37 takes over the products-completed operations hazard later. Many contracts require keeping the completed-operations endorsement for years after work is done.
This guide is for educational purposes and summarizes standard ISO policy language. Your policy's specific terms, conditions, and endorsements control. Talk to a licensed broker about your actual exposures.
The Bottom Line
If you give an additional insured endorsement to your business partner, they will get insured status under your CGL policy. However, it will only be up to how far that particular type of endorsement (the form number) goes. The CG 20 10 endorsements cover your ongoing operations, while the CG 20 37 endorsements cover your completed operations. Neither of these types of endorsements would provide coverage for your business partner's sole negligence, nor would they increase your overall limit of liability. Obtain the endorsement schedule. Read what each endorsement says. Compare that to your contract, specifically the exhibit regarding insurance. Make sure there is a signed document by both parties prior to beginning work.
References
- 1.California Legislative Information. “Civil Code Section 2782.” Accessed July 2026. https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=CIV§ionNum=2782 ↩
- 2.New York Court of Appeals. “Gilbane Bldg. Co. v. St. Paul Fire and Marine Ins. Co., 31 N.Y.3d 131 (2018).” Accessed July 2026. https://case-law.vlex.com/vid/gilbane-bldg-co-v-886781872 ↩