Cg 20 01 Primary Noncontributory Explained: Key Insights for Brokers

The ISO endorsement CG 20 01 primary noncontributory is one of the most frequently required and most frequently mishandled provisions in commercial GL coverage. According to ACORD 2024, 71% of commercial construction contracts require primary and non-contributory additional insured status. Yet a significant share of certificates issued against those contracts contain errors in how the endorsement is documented or confirmed.

This guide explains what CG 20 01 does, how it interacts with standard GL policy language, what it costs, and exactly how to document it on an ACORD 25 certificate.

Key Takeaways

• ISO CG 20 01 is the "Additional Insured - Owners, Lessees, or Contractors - Primary and Noncontributory" endorsement; it modifies the named insured's GL policy to make coverage primary and non-contributory with respect to the additional insured's own policy.
• Without CG 20 01, standard GL language makes both the sub's and GC's policies co-equal primary policies, which triggers a contribution dispute and delays claim resolution by an average of 5 to 8 months (IIABA 2025).
• CG 20 01 activates only when a written contract requires primary and non-contributory status; without that contract, the endorsement has no effect.
• ACORD 2024 data shows 71% of commercial construction contracts require primary and non-contributory AI coverage, making this one of the most common endorsement requirements brokers manage.
• The endorsement typically costs 2 to 5% of the GL premium; some carriers bundle it into blanket AI packages at no additional charge.
• Primary and non-contributory status must be documented in the Description of Operations field on the ACORD 25; there is no checkbox for it on the face of the form.

What CG 20 01 Is

The full ISO form title is "Additional Insured - Owners, Lessees, or Contractors - Primary and Noncontributory." ISO introduced the form to give additional insureds a clear contractual mechanism to control how coverage responds when a shared loss occurs.

The endorsement modifies the named insured's commercial general liability policy in two specific ways. First, it makes the named insured's policy primary with respect to the additional insured's own liability coverage. Second, it makes the named insured's policy non-contributory, meaning the named insured's insurer will not seek contribution from the additional insured's insurer.

Both modifications activate only when required by a written contract between the named insured and the additional insured.

The Two Concepts the Endorsement Creates

Primary Coverage

"Primary" means the named insured's policy pays first, before the additional insured's own GL policy is triggered. This matters because standard GL language says coverage is "primary except when it is excess over other available coverage." When two policies both contain that standard language and both parties are named insureds on their own policies, neither carrier wants to pay first.

The result without CG 20 01 is a "battle of the insurers." Both carriers dispute which policy is primary. The GC's own policy is dragged into a claim that arose from the sub's work. Claims payments are delayed, often by months.

With CG 20 01 on the sub's policy, the sub's insurer accepts primary responsibility. The GC's own policy sits in excess position and is not triggered unless the sub's limits are exhausted.

Noncontributory Coverage

"Noncontributory" means the named insured's insurer will not demand that the additional insured's insurer contribute to the loss. Even if the additional insured has its own GL policy with available limits, the sub's carrier cannot require the GC's carrier to share the payment.

This distinction matters most in large claims where the sub's limits are at risk of being exhausted. Without the non-contributory element, the sub's carrier will seek contribution from the GC's carrier. With it, the GC's insurer sits on the sideline unless the sub's limits are fully exhausted.

Why CG 20 01 Matters: The Without-vs.-With Scenario

To see the practical effect, consider a $300,000 claim arising from a subcontractor's work on a project where the GC is named as additional insured on the sub's policy.

Without CG 20 01:

• Sub's GL policy: $1,000,000 per occurrence
• GC's GL policy: $1,000,000 per occurrence
• Both policies have the standard "primary except when excess" language
• Both carriers assert their policy is excess; neither pays voluntarily
• A court or arbitration panel eventually apportions the loss
• Each carrier pays $150,000 (50% share)
• The GC's loss history is affected by a $150,000 payment
• The GC's renewal premium increases
• Claims resolution takes 8 to 18 months (IIABA 2025)

With CG 20 01 on the sub's policy:

• Sub's carrier accepts primary responsibility immediately
• Sub's carrier pays the full $300,000
• GC's carrier does not respond; the GC's limits are untouched
• The GC's loss history is unaffected
• Claims resolution proceeds in 2 to 4 months

The financial impact on the GC is material. Its limits remain available for other claims, and its loss experience does not drive a premium increase.

Claim Handling Comparison Table

Source: IIABA 2025 claims handling data. Figures represent industry benchmarks for a $300,000 construction GL claim.

Who Requires CG 20 01

General contractors require CG 20 01 on virtually all subcontractor GL policies in commercial construction. This is standard language in AGC contract templates and is also found in AIA contract forms.

Commercial landlords require it on tenant GL policies when the lease creates liability exposure for the landlord. Government contracting agencies require it in most construction and services agreements. Franchise agreements increasingly include primary and non-contributory language as a standard requirement for franchisees.

ACORD 2024 reports that 71% of commercial construction contracts now require primary and non-contributory AI coverage. That figure was 54% in 2019. The requirement has migrated from large GC contracts to smaller commercial service agreements as well.

The Written Contract Requirement

CG 20 01 does not apply automatically across all additional insured relationships. The endorsement contains specific language: primary and non-contributory status applies "where required by a written contract." Without that written contract, the standard GL policy language governs how two policies interact when a shared loss occurs.

This creates a practical obligation for brokers. Before confirming that CG 20 01 is in effect for a specific project or relationship, the broker must confirm that a written contract exists between the named insured and the additional insured that contains the required language. A verbal agreement or purchase order without the explicit language is not sufficient.

How to Note P&NC on the COI

The ACORD 25 certificate of insurance does not have a checkbox for primary and non-contributory status. There is no box to check. The documentation belongs in the Description of Operations field (Box 23 on the ACORD 25-2016).

The recommended notation is:

"Coverage under [Insurer Name] Policy [Policy Number] is primary and non-contributory per ISO CG 20 01 where required by written contract."

What is not acceptable: "Additional insured as required by contract." That language confirms AI status only. It says nothing about primary and non-contributory.

Some certificate holders provide their own required language for the DOO. Always use the language the certificate holder specifies if it is contractually required and does not misrepresent the actual endorsement.

Do not check any box on the ACORD 25 face to indicate P&NC. No such checkbox exists. Checking an incorrect box creates a misrepresentation on the certificate.

Cost of the CG 20 01 Endorsement

The endorsement typically adds 2 to 5% to the GL premium for standard commercial classes. For a policy with a $10,000 annual GL premium, the endorsement cost runs $200 to $500 per year.

Some carriers include CG 20 01 in blanket additional insured packages at no additional charge. When a blanket AI endorsement includes primary and non-contributory language, the broker should confirm the exact form number and confirm that the blanket form provides the same protection as the scheduled CG 20 01.

High-hazard classes face higher costs or carrier declinations. Some admitted carriers will not add CG 20 01 for roofing, demolition, or scaffolding contractors. Excess and umbrella carriers frequently decline to follow the underlying primary and non-contributory endorsement unless they are specifically endorsed to do so.

Does Blanket AI Automatically Include P&NC?

No. Additional insured status and primary and non-contributory status are separate provisions. A blanket AI endorsement (such as CG 20 10 04 13 or CG 20 37 04 13) gives a third party coverage under the named insured's policy. It does not automatically make that coverage primary and non-contributory.

To have both, the policy needs both:

1. An AI endorsement (scheduled or blanket) that adds the GC, landlord, or other party as an additional insured
2. CG 20 01 (or a blanket endorsement that incorporates primary and non-contributory language) that makes that coverage primary and non-contributory

Some carriers offer a combined endorsement that does both in one form. If a carrier uses its own form rather than the ISO CG 20 01, the broker should review the form language to confirm it provides equivalent protection.

Carrier Limitations to Watch For

Several carrier positions create compliance gaps for brokers managing construction accounts:

Admitted carriers for high-hazard classes sometimes decline to add CG 20 01 or will add it only with prior underwriting approval. If a sub's carrier declines, the broker needs to notify the GC before the sub begins work.

Excess and umbrella carriers: most will not automatically follow the underlying GL's primary and non-contributory endorsement. The umbrella policy needs its own P&NC endorsement if the contract requires it at the umbrella level.

Completed operations: some carriers will add CG 20 01 for ongoing operations but decline for completed operations. This creates a coverage gap for claims that arise after project completion. ISO CG 20 37 addresses completed operations AI, and the P&NC endorsement must also apply to that period to be fully effective.

Frequently Asked Questions

What does ISO CG 20 01 do and when is it required?

ISO CG 20 01 modifies the named insured's commercial general liability policy to make coverage primary and non-contributory with respect to an additional insured's own liability policy. It is required when a written contract between the named insured and the additional insured contains language specifying that the named insured's coverage must be primary and non-contributory. Without that written contract, the endorsement has no effect even if it appears on the policy.

What is the difference between "primary" and "noncontributory" in an insurance context?

"Primary" means the named insured's policy pays before the additional insured's own policy is triggered. "Noncontributory" means the named insured's insurer will not seek contribution from the additional insured's insurer when a covered loss occurs. The two concepts work together: primary establishes the payment order, and noncontributory prevents the named insured's carrier from pulling the additional insured's carrier into the claim.

What does a GL policy without CG 20 01 do when a shared claim arises?

Standard GL policy language says coverage is "primary except when it is excess over other available coverage." When both the named insured and the additional insured have policies with that language, neither carrier accepts primary responsibility automatically. The result is a coverage dispute between the two insurers. Both carriers may share the loss proportionately, delay payment while the dispute is resolved, or litigate the question of which policy is primary. IIABA 2025 data shows these disputes add 5 to 18 months to claim resolution timelines.

How is primary and non-contributory shown on an ACORD 25 certificate?

P&NC status goes in the Description of Operations field (Box 23 on the ACORD 25-2016). There is no checkbox on the face of the form for it. The notation should identify the specific endorsement: "Coverage is primary and non-contributory per ISO CG 20 01 where required by written contract." Do not use "additional insured as required by contract" as a substitute. That language documents AI status only, not P&NC.

How much does the CG 20 01 endorsement cost?

For standard commercial classes, the endorsement typically adds 2 to 5% to the GL premium. A $10,000 GL premium generates an endorsement cost of $200 to $500 per year. Some carriers include CG 20 01 in blanket AI packages at no additional charge. High-hazard classes may face higher costs, carrier declinations, or prior approval requirements. Excess and umbrella carriers typically charge separately if they agree to add primary and non-contributory status at all.

Does CG 20 01 apply automatically when blanket AI is on the policy?

No. Blanket AI endorsements add additional insured status but do not change how coverage responds relative to the AI's own policy. CG 20 01 must be on the policy separately, or the blanket AI endorsement must explicitly include primary and non-contributory language in its text. Always confirm the specific form language rather than assuming blanket AI equals primary and non-contributory. Some carriers use proprietary blanket AI forms that include P&NC language; others do not. Check the actual endorsement.

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