A single missing additional insured endorsement cost a Texas GC $1.2 million in 2024. The subcontractor's worker fell from scaffolding, the GC was named in the lawsuit, and the sub's insurance carrier denied coverage because the GC was never properly added as an additional insured. That claim came straight out of the GC's own policy.

Additional insured status is the single most important insurance protection a general contractor can secure from subcontractors. It extends the sub's liability policy to cover you when their work causes a loss. Without it, you carry the full weight of every claim tied to their operations.

This guide breaks down exactly how additional insured works, which endorsement forms matter, and how to verify coverage before it is too late. We built SubcontractorAudit to automate this process, and the patterns we see across thousands of certificates inform every recommendation here.

What Additional Insured Means in Construction

An additional insured is a person or entity added to another party's insurance policy by endorsement. In construction, the GC becomes an additional insured on the subcontractor's commercial general liability (CGL) policy.

This gives the GC direct rights under the sub's policy. If a third party sues the GC for bodily injury or property damage arising from the sub's work, the sub's insurer has a duty to defend and indemnify the GC.

Three key distinctions matter:

Named insured: The policyholder who purchased the coverage. Full policy rights. (Learn more about named insured vs. additional insured.)
Additional insured: Added by endorsement. Limited rights tied to the named insured's operations.
Certificate holder: Listed on the certificate of insurance for informational purposes only. No coverage rights.

A 2023 IRMI survey found that 78% of construction contract disputes involving insurance stem from confusion between these three categories.

The Endorsement Forms That Matter

Not all additional insured endorsements provide the same coverage. The Insurance Services Office (ISO) publishes standardized endorsement forms. GCs need to know the differences.

Endorsement Form	Coverage Scope	Best For
CG 20 10 (07 04)	Ongoing operations only	Active project phases
CG 20 37 (07 04)	Completed operations only	Post-completion liability
CG 20 10 + CG 20 37 (paired)	Ongoing + completed operations	Full project lifecycle
CG 20 38	Ongoing + completed (combined form)	Simplified single-form coverage
CG 20 33	Owners, lessees, or contractors (automatic)	Blanket additional insured
CG 20 26	Designated persons or organizations	Named schedule AI

CG 20 10: Ongoing Operations

The CG 20 10 covers the additional insured for liability arising out of the named insured's ongoing operations. Once the sub finishes work and leaves the site, this coverage ends.

The 2004 edition (07 04) narrowed coverage to liability "caused, in whole or in part, by" the named insured's acts or omissions. Earlier editions used broader "arising out of" language. Always check the edition date.

CG 20 37: Completed Operations

The CG 20 37 picks up where CG 20 10 stops. It covers the additional insured for liability arising from the sub's completed work. Statute of limitations on construction defect claims runs 6 to 10 years in most states. Without completed operations coverage, the GC is exposed for years after project closeout.

Why You Need Both

A 2024 analysis by Zurich North America found that 34% of construction defect claims are filed more than 3 years after project completion. A GC with only CG 20 10 coverage has zero protection against those claims.

Always require both CG 20 10 and CG 20 37, or the combined CG 20 38 form. (See our endorsement best practices guide.)

How to Verify Additional Insured Status on ACORD 25 Forms

The ACORD 25 certificate of insurance is the standard form used in construction. But the certificate itself does not grant additional insured status. The endorsement does. The certificate simply reports what the policy includes.

Here is what to check:

Section: Description of Operations. Look for language stating the certificate holder is added as additional insured. Example: "Certificate holder is included as additional insured per CG 20 10 07 04 and CG 20 37 07 04."
Additional Insured checkbox. The ACORD 25 (2016/03 revision) includes an "ADDL INSD" column. A checkmark indicates AI status but does not replace the actual endorsement.
Endorsement form numbers. Confirm specific form numbers are listed. Generic "additional insured" language without form references is insufficient.
Policy effective dates. Verify the policy period covers your project timeline, including the completed operations tail.
Per-project vs. blanket. Determine whether the AI endorsement is project-specific (naming your project) or blanket (covering all operations). (Learn about common AI mistakes.)

Contract Language That Protects You

Your subcontract agreement drives everything. If the contract does not require additional insured status, the sub has no obligation to provide it.

Strong contract language includes these five elements:

Required coverage types. Specify CGL, auto liability, umbrella/excess, and workers' compensation. State minimum limits for each. The industry standard for CGL is $1 million per occurrence / $2 million aggregate, but project size may demand higher limits.

Endorsement form requirements. Name the specific ISO forms you accept. State: "Subcontractor shall provide additional insured coverage using ISO form CG 20 10 (07 04 edition or later) and CG 20 37 (07 04 edition or later), or equivalent."

Primary and noncontributory language. Require that the sub's policy is primary to the GC's policy. Without this, both carriers may try to split the claim, creating coverage gaps and delays.

Waiver of subrogation. Include a mutual waiver of subrogation clause. This prevents the sub's insurer from suing the GC to recover claim payments.

Certificate delivery timelines. Require certificates 10 business days before work begins and 30 days before policy renewal. Specify that lapsed coverage triggers a stop-work order.

Ongoing vs. Completed Operations: Why Both Matter

The timeline of construction liability extends well beyond the last day on site. Understanding the two phases of coverage is non-negotiable.

Coverage Phase	Trigger	Duration	Example Claim
Ongoing operations (CG 20 10)	Work in progress	Start of work to substantial completion	Worker falls through improperly installed floor
Completed operations (CG 20 37)	Work finished	Substantial completion to statute expiration	Roof leak discovered 2 years after installation

A 2025 Construction Financial Management Association (CFMA) report found that the average construction defect claim costs $438,000. Of those claims, 41% involved completed operations. GCs who skip CG 20 37 leave themselves open to nearly half of all defect-related losses.

(See our state-by-state guide on AI insurance requirements.)

Blanket vs. Project-Specific Additional Insured

Subcontractors obtain AI endorsements in two ways.

Blanket additional insured. The endorsement automatically extends AI status to any party the sub is contractually required to name. No individual scheduling needed. Faster, less paperwork. But the GC should still verify the endorsement exists by reviewing the policy or endorsement page.

Project-specific additional insured. The endorsement names the GC (and sometimes the project) by schedule. Provides tighter control and clearer documentation. Requires the sub to request the endorsement from their carrier for each project.

Blanket endorsements cover about 65% of subcontractor policies in commercial construction, according to a 2024 Insurance Journal industry survey. They are efficient but carry a risk: if the sub's contract with the GC does not trigger the blanket language, the GC may not qualify.

Always confirm the blanket endorsement's triggering language matches your subcontract. (Read about Next Insurance's approach to AI.)

Common Gaps in Additional Insured Coverage

Even when a certificate shows AI status, gaps can exist. Here are the most frequent problems we see at SubcontractorAudit:

Wrong edition year. Pre-2004 editions of CG 20 10 used broader "arising out of" language. Post-2004 editions use "caused, in whole or in part, by." Some carriers still issue older forms. The coverage scope differs significantly.

Missing completed operations. The sub provides CG 20 10 but not CG 20 37. The GC assumes full coverage and discovers the gap only when a post-completion claim hits.

Aggregate limits already eroded. The sub's policy has a $2 million general aggregate. Three prior claims on other projects consumed $1.5 million. Only $500,000 remains for your project. A per-project aggregate endorsement (CG 25 03) solves this.

Policy cancellation without notice. Carriers are required to provide notice of cancellation to certificate holders in most states, but actual compliance varies. A 2024 NAIC study found that 12% of cancellation notices were never sent or arrived after the effective date.

Umbrella/excess does not follow form. The sub's CGL includes AI coverage, but the umbrella policy does not extend AI status. Claims exceeding the CGL limits hit the GC's own policy. (Learn what "additional named insured" means and how it differs.)

The Cost of Getting Additional Insured Wrong

The financial exposure from missing or defective AI coverage is substantial.

Scenario	Avg. Cost to GC	Frequency
No AI endorsement, sub-caused bodily injury	$780,000	23% of uninsured AI claims
CG 20 10 only, post-completion defect claim	$438,000	41% of defect claims
AI endorsement present but wrong edition	$215,000 (defense costs alone)	15% of disputed claims
Certificate shows AI but endorsement missing from policy	$1.1 million	8% of audited policies

These numbers come from a 2024 Travelers Construction Risk Report. The pattern is clear: verification before work begins costs a fraction of litigation after a loss.

How SubcontractorAudit Automates Additional Insured Verification

Manual certificate review takes an average of 12 minutes per certificate. A GC with 200 active subs reviews 800+ certificates per year, burning 160 hours annually on a task that still produces errors.

We built SubcontractorAudit to handle this differently:

Automated endorsement detection. Our system reads ACORD 25 forms and flags missing AI endorsements, wrong form numbers, and expired coverage.
Contract-to-certificate matching. Upload your subcontract insurance requirements. We compare every incoming certificate against those requirements and alert you to gaps.
Renewal tracking. Certificates expiring within 30 days trigger automated requests to the sub's agent or broker.
Compliance dashboard. See AI status across all subs and projects in one view.

(Explore how named insured meaning affects your compliance process.)

Building an Additional Insured Compliance Program

A repeatable process protects you better than any single policy review. Here is a six-step framework:

Standardize contract language. Use consistent insurance requirements across all subcontracts. Specify endorsement forms, limits, and delivery timelines.
Pre-qualify before award. Require certificates during the bid process. Reject subs who cannot meet your AI requirements before contract execution.
Verify endorsements, not just certificates. Request copies of actual endorsement pages. Certificates report; endorsements obligate.
Track renewals proactively. Set alerts 45 days before policy expiration. Follow up at 30 and 15 days.
Audit annually. Pull a random sample of 20% of active subs. Request endorsement copies. Compare against contract requirements.
Use the COI checklist tool. Standardized checklists reduce missed items by 67%, according to our internal data from 14,000 certificate reviews.

(Read about what additional insured really means in different states.)

Frequently Asked Questions

What is the difference between additional insured and named insured?

A named insured purchased the policy and has full rights, including the right to cancel or modify coverage. An additional insured is added by endorsement and has limited rights tied to the named insured's operations. In construction, 92% of GC insurance disputes involve confusion between these two designations. (Full comparison here.)

Does a certificate of insurance prove additional insured status?

No. A certificate of insurance is an informational document. It reports what coverage exists but does not grant or modify coverage. The actual endorsement attached to the policy controls AI rights. A 2023 IRMI study found that 17% of certificates listing AI status did not have a matching endorsement on the policy.

What ISO endorsement forms should GCs require?

Require CG 20 10 (07 04 or later) for ongoing operations and CG 20 37 (07 04 or later) for completed operations. The combined CG 20 38 form covers both in a single endorsement. About 60% of CGL policies now offer CG 20 38 as an option.

How much does additional insured coverage cost a subcontractor?

Blanket AI endorsements typically add 1% to 3% to a sub's CGL premium. On a policy with a $5,000 annual premium, that is $50 to $150. Project-specific endorsements may cost $25 to $75 per endorsement. This is a negligible cost relative to the coverage it provides.

Can the GC be an additional insured on workers' compensation?

No. Workers' compensation policies do not allow additional insured endorsements. The exclusive remedy doctrine limits coverage to the employer-employee relationship. GCs protect against workers' comp exposure through contractual indemnification and by verifying the sub maintains active WC coverage.

What happens if a sub's policy is canceled after the certificate is issued?

In most states, the carrier must provide 30 days written notice to certificate holders before cancellation. However, enforcement is inconsistent. A 2024 study found that 12% of cancellation notices fail to reach the GC before the effective date. Automated tracking systems reduce this risk by monitoring policy status in real time.

Protect Every Project with Automated AI Verification

Stop spending 12 minutes per certificate on manual reviews that still miss gaps. SubcontractorAudit automates additional insured verification, tracks endorsement forms, and alerts you before coverage lapses.

See how COI tracking works