The Additional Insured Endorsement: Why ISN Keeps Rejecting Your COI

You sent the certificate. The box for "Additional Insured" is checked. The description says the hiring client is named as additional insured. ISN still rejects it. Your client is asking when you'll be compliant. Your broker says it's fine.

Everyone is looking at a different piece of paper. Here is what is actually happening, why roughly nine out of ten additional-insured-related COI rejections land for the same reason, and exactly what to send back so ISN clears the requirement the first time.

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The Certificate Is Not the Endorsement

A certificate of insurance (the ACORD 25 form) is a summary. It says "this policy exists, here are the limits, here is who we say is additional insured." It is issued by your broker, not your insurance carrier. It is evidence of coverage, not coverage itself.

An endorsement is a document issued by the carrier that modifies the policy. The additional insured endorsement is the only thing that actually extends coverage to your hiring client. The certificate references it. It does not replace it.

When ISN says "we need the additional insured endorsement," they mean the actual endorsement form attached to the policy — not the checkbox on the ACORD 25. This is the single most common source of COI rejection in the platform.

The ACORD 25 even spells it out in its own footer: "This certificate does not confer rights upon the certificate holder." That line exists because hiring clients kept assuming the certificate was the coverage. It is not.

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What ISN Is Actually Checking

ISN's COI review workflow verifies three things against the client's requirements:

1. The ACORD 25 shows the hiring client listed as additional insured.
2. An endorsement form (CG 20 10, CG 20 37, or an equivalent) is attached to the COI package.
3. The endorsement names the hiring client, covers both ongoing and completed operations, and — for many clients — is on a primary and non-contributory basis.

Miss any one of those and the COI goes back as rejected. Most of the time it's item two: the endorsement was never requested from the carrier, was never attached to the PDF package, or the wrong form was sent.

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CG 20 10 vs CG 20 37: The Difference That Gets You Rejected

ISO publishes the standard additional insured endorsement forms that most commercial general liability carriers use. Two of them come up constantly in construction work. They sound similar. They do different things.

CG 20 10 — Ongoing Operations

The CG 20 10 endorsement extends additional insured status for liability arising out of your ongoing operations performed for the hiring client. "Ongoing" means work that is in progress. If a subcontractor's employee slips on the jobsite while the project is still active and sues the general contractor, the CG 20 10 responds.

What it does not cover: claims that arise after the project is complete. If a building you framed two years ago collapses and the owner sues the GC, CG 20 10 alone is silent.

CG 20 37 — Completed Operations

The CG 20 37 endorsement extends additional insured status for liability arising out of "your work" included in the products-completed operations hazard. That is the coverage that responds after the job is finished and your crew has left.

Virtually every sophisticated hiring client — general contractors, facility owners, energy majors, utilities — requires both. If you send only the CG 20 10, you've covered half the exposure. ISN will flag it and kick the COI back.

The "CG 20 10 10 01" trap

Here's where it gets nastier. ISO revises these forms over time, and each edition has a date suffix. The CG 20 10 10 01 (the October 2001 edition) used to include completed operations coverage in the same form. The CG 20 10 07 04 (July 2004) and later editions stripped it out. If your carrier is on any edition from 2004 forward, the CG 20 10 covers ongoing operations only, and you need the separate CG 20 37.

Rule of thumb: unless your broker can prove in writing that your CG 20 10 is the pre-2004 edition with completed operations baked in, assume you need both CG 20 10 and CG 20 37. Don't argue with ISN about editions — just send both.

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Primary and Non-Contributory: The Third Requirement

Most major hiring clients require that your coverage respond primary and non-contributory with respect to any insurance the hiring client carries on its own. Translation: if there's a claim, your policy pays first, and your carrier cannot chase the hiring client's carrier to split the bill.

That wording is almost never baked into the CG 20 10 or CG 20 37 by default. It gets added via a separate endorsement — commonly CG 20 01 (Primary and Noncontributory — Other Insurance Condition) or a carrier-proprietary equivalent.

When ISN's COI review asks whether coverage is "primary and non-contributory," they're looking for that endorsement in the package or the policy language that makes it so. Checking the box on the ACORD 25 without an underlying endorsement is the same failure mode all over again.

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Blanket Endorsements: Convenient, Not Always Enough

Many carriers now issue blanket additional insured endorsements. Instead of naming each client individually, the form grants additional insured status to "any person or organization whom you are required to add as an additional insured under a written contract."

Blanket forms are a legitimate way to satisfy the requirement, and ISN will accept most of them. Two things to watch:

• The blanket must cover completed operations. If it's ongoing-ops only, you're back to the CG 20 10 vs CG 20 37 problem.
• There must be a written contract or executed PO before the loss. Blanket forms only grant additional insured status if a written agreement requiring it exists. A verbal handshake doesn't trigger coverage.

If you rely on a blanket, send ISN the full endorsement form with the package, not just a line on the ACORD 25 that says "blanket additional insured per written contract." Reviewers need to verify the scope.

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Waiver of Subrogation: Bundled in the Same Fight

Almost every client that requires additional insured status also requires a waiver of subrogation on the same policies. Subrogation waivers are issued via separate endorsements (CG 24 04 on general liability, WC 00 03 13 on workers' comp) and live or die by the same certificate-vs-endorsement distinction.

For a walkthrough of what subrogation is, why clients require the waiver, and how the WC 00 03 13 form works, see Waiver of Subrogation Explained for Contractors (Without the Legal Jargon).

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The Exact Package ISN Wants

When you ask your broker for a "COI package for [Hiring Client Name] through ISNetworld," this is the complete bundle you should receive back — not just the ACORD 25:

1. ACORD 25 Certificate of Liability Insurance — hiring client listed as certificate holder and additional insured in the description.
2. CG 20 10 (current edition) — ongoing operations additional insured endorsement.
3. CG 20 37 — completed operations additional insured endorsement.
4. CG 20 01 or equivalent — primary and non-contributory endorsement.
5. CG 24 04 — waiver of subrogation on general liability.
6. WC 00 03 13 — waiver of subrogation on workers' comp (blanket or scheduled, matching the client requirement).
7. Auto equivalents — CA 20 48 (additional insured) and CA 04 44 (waiver of subrogation) on the commercial auto policy if the client requires it.
8. Umbrella/excess follow-form endorsement — showing the umbrella sits over the underlying policies and extends additional insured and waiver status upward.

That is a real package. It is usually six to twelve PDF pages, not one.

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Why Brokers Sometimes Push Back

When you ask your broker for individual endorsement forms, you'll occasionally hear "the blanket on the policy already covers this" or "the certificate is sufficient." Sometimes that's true. Often it's shorthand for "pulling those forms takes me thirty minutes and I'd rather not."

Your job isn't to argue coverage law. Your job is to hand ISN a package that matches their checklist. If the blanket endorsement truly covers the requirement, ask for the actual endorsement form — not a broker letter summarizing it. ISN reviewers need to read the form, not take anyone's word for it.

If your broker cannot produce the endorsement forms on demand, that is a signal worth paying attention to. Every well-run commercial lines broker has them a click away in AMS360, Applied Epic, or the carrier's portal.

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When the Rejection Hits: A Five-Minute Response

ISN flagged the COI. The hiring client's PM emailed you. You have one day to fix it. Here's the compressed workflow:

1. Read the rejection reason. ISN tells you which requirement failed. If it says "additional insured endorsement missing," you need the form, not a new certificate.
2. Email your broker the exact language. "ISN rejected our COI for [Client]. They need CG 20 10 and CG 20 37 endorsements attached, primary and non-contributory wording, and confirmation that the blanket covers completed operations. Please send the full package."
3. Upload the complete PDF to ISN. One file, all forms, ACORD 25 on top. Do not upload the endorsements as a separate document unless ISN's interface forces you to.
4. Confirm receipt with the hiring client's PM. A two-sentence email closes the loop and pulls you out of the "noncompliant" column on their internal dashboard.

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Don't Wait for the Rejection

The contractors who never see these rejections are the ones who requested the full endorsement package the day the contract was signed — not the day ISN flagged it. Build it into your onboarding: every new hiring client gets a COI package request that names all six or seven forms by number, not a vague "please issue a COI."

Your broker will do the work either way. The only question is whether you spend Tuesday arguing with a project manager, or spend Monday sending one email and being done.