What is an additional insured endorsement? (GC guide)

General contractors routinely require additional insured status on subcontractor general liability policies. Reviewers see the checkbox on the certificate, approve the file, and move on. Later, a claim or audit reveals the underlying endorsement was never issued, named the wrong entity, or expired at renewal. Understanding what an additional insured endorsement actually is, and how it differs from COI language, is core GC compliance work.

This guide defines the endorsement, contrasts it with certificate summaries, and gives reviewers a practical verification list before clearing a sub for mobilization.

Build a baseline endorsement package with the insurance requirements generator, then verify form numbers on each COI.

What is an additional insured endorsement?

Additional insured endorsement: A policy amendment that adds one or more parties to the subcontractor's liability coverage as additional insureds, within the limits and conditions stated on the endorsement form.

The endorsement modifies the subcontractor's general liability policy. It specifies:

• Who is added (GC legal name, owner, lender, or other parties required by contract).
• Which coverage extends to those parties (often ongoing operations and completed operations for construction).
• Which form applies (ISO CG 20 10, CG 20 37, or carrier proprietary equivalent).
• Effective dates aligned with the policy term.

If your owner contract references specific ISO editions, store those references in your requirement template so reviewers do not accept outdated forms at renewal.

Contracts transfer risk in part by requiring the sub's policy to respond for certain claims involving the GC or owner. The endorsement is the instrument that effectuates that transfer on the policy itself. Without it, certificate language alone may not deliver the protection your contract assumes.

How is it different from what appears on the COI?

The certificate of insurance (ACORD 25) is a snapshot prepared by the broker. It can indicate that additional insured status applies and may list form numbers in the description box. It is not the endorsement and it is not the policy.

GC teams should treat COI additional insured language as a pointer, not proof. Proof is a current endorsement (or policy provision, when applicable) that names your entity and matches approved form numbers.

Common gaps at renewal:

• Endorsement dropped when the sub changed brokers.
• Form edition changed and no longer matches owner requirements.
• Named insured on the endorsement uses an old LLC name after a merger.

Train project teams that "additional insured on the COI" is a starting point, not approval. Coordinators should attach the endorsement PDF to the vendor record and note the form number in the clearance log so audits do not depend on memory.

What should GC reviewers check before clearing a sub?

Before mobilization, verify additional insured requirements in this order:

1. Contract requirement: Identify which parties need additional insured status (GC, owner, lender) and which form numbers or equivalent language the owner accepts.
2. COI review: Confirm the certificate lists the correct named insured, policy dates, and additional insured indication with form references when provided.
3. Endorsement review: Obtain and file the endorsement. Confirm parties, form number, edition, and effective dates match requirements.
4. Renewal check: On every renewal COI, reconfirm the endorsement was reissued and did not drop off.
5. Clearance log: Record verification date and reviewer so audits can reconstruct the decision.

When owners require primary and non-contributory language alongside additional insured status, verify those terms on the endorsement or policy form, not only in the subcontract exhibit.

Pair this review with the broader subcontractor insurance requirements checklist. For ongoing monitoring, integrate endorsement checks into COI tracking for general contractors so renewals trigger re-verification.

When your program needs a walkthrough of requirement templates and review workflows, request a demo.

Keep a scanned or PDF copy of each endorsement with the COI in the same vendor folder so reviewers do not search attachments at mobilization time.