Additional Insured Endorsement: Why Contracts Require It

Last updated August 2026.

Your contract says the vendor must name you as an additional insured. Their certificate of insurance shows coverage. Those are not the same thing, and the gap between them is where a covered loss quietly becomes your problem. An additional insured endorsement is the piece that actually extends a vendor's policy to protect you, and confirming it is on every certificate is one of the most overlooked steps in insurance compliance. This guide explains what the endorsement is, why contracts require it, and how to verify you actually have it.

What an additional insured endorsement is

An additional insured endorsement is an amendment to a policy that extends its coverage to a party other than the named policyholder. When a vendor adds you as an additional insured on their general liability policy, their insurer agrees to defend and indemnify you for claims arising out of the vendor's work. Without it, you are a stranger to that policy: even if the vendor caused the loss, their insurer has no obligation to you, and you are left to pursue them and pay your own defense in the meantime. Setting that expectation in writing before work starts is part of defining your vendor insurance requirements.

Why contracts require it

Requiring additional insured status is how you push the risk of a vendor's work back onto the party creating it. If a subcontractor's crew causes injury or damage, you want their insurer responding first, not your own policy taking the hit and your loss history paying for it later. That is why well-written vendor agreements, and nearly every commercial lease, require the other party to name you as additional insured, often with a waiver of subrogation alongside it. Commercial leases are the clearest example, which is why the insurance commercial landlords require from tenants almost always starts with additional insured status. The requirement is only worth anything if the endorsement is actually issued and on file.

The trap: a certificate is not the endorsement

Here is where compliance quietly fails. A certificate of insurance is a summary, and the box that says "additional insured" on a certificate is informational. Our field-by-field walkthrough of the ACORD 25 form shows exactly where that wording sits and why it carries no coverage on its own. It does not, by itself, grant you anything. The coverage is granted by the endorsement attached to the policy. A certificate can show the box checked while no endorsement was ever issued, and you would not know until a claim, when the insurer points out you were never actually added. Confirming the endorsement, not just the checkbox, is the whole job.

Which additional insured endorsement does your contract need?

The right form depends entirely on the relationship, and using the wrong one is a quiet failure because the paperwork still looks complete. Construction work performed for you takes CG 20 10 for ongoing operations and CG 20 37 for completed operations, or the blanket equivalents. A tenant naming a landlord takes CG 20 11, written for managers or lessors of premises. A party who never hired the vendor at all, such as a municipality issuing a permit, takes CG 20 26. Each of these is a different ISO form with a different grant, and they are listed side by side in the additional insured endorsement forms reference.

The mismatch that comes up most often is a construction form used for a lease. A landlord who demands CG 20 10 from a retail tenant is asking for coverage keyed to operations the tenant performs for the landlord, which is usually nothing. The endorsement gets issued, everyone files it, and it covers almost none of the exposure the landlord was actually worried about. Landlords running more than a handful of tenancies usually catch this by abstracting the insurance clause out of each lease first, so the form they demand matches what the lease actually says.

Why the edition date on the endorsement matters

The digits printed after the form number are the edition date, and they change what the form does. The 11 85 edition of CG 20 10 covered both ongoing and completed operations under one form. Every edition from 10 01 onward covers ongoing operations only, which is why CG 20 37 exists as a separate endorsement. The 04 13 edition went further and added two limitations: coverage applies only to the extent permitted by law, and it can never be broader than what your own contract required, with the payout capped at the lesser of the contract-required amount or the policy limits.

That last point is the one worth acting on. From 2013 onward your own insurance requirements clause sets the ceiling on your coverage. If your template asks for $1 million and the vendor carries $5 million, you have $1 million. A template inherited from a decade ago is quietly capping every additional insured position you hold. The full edition history is in CG 20 10 edition dates.

What to do when a vendor cannot provide the endorsement

Sometimes the answer is genuine. A vendor on a small business owners policy may not have the ISO general liability forms available at all, and no amount of chasing will produce a CG 20 37 that the carrier does not write. Distinguish that from the far more common case, which is that the vendor never asked their agent.

Ask the vendor to forward the request to their agent in writing, naming the form. Agents produce endorsements quickly when the request is specific and slowly when it is vague, which is why "we need CG 20 37 completed operations additional insured status naming Acme Holdings LLC" works and "your COI is non-compliant" does not. If the carrier genuinely will not issue it, you are making a business decision rather than a paperwork one: accept the gap knowingly, require higher limits or a different structure, or use a different vendor. What you should not do is record the vendor as compliant because the file has a certificate in it.

How to verify you are actually covered

For each vendor whose contract requires it:

• Get the endorsement form, not just the certificate (commonly a CG 20 10, CG 20 37, or a blanket additional insured form), and keep it on file with the certificate. The two standard forms cover different phases of the work, which our comparison of CG 20 10 vs CG 20 37 explains.
• Check it names you specifically or via a blanket "where required by written contract" wording that matches your agreement.
• Confirm it is current for the policy period the work happens in, and re-confirm at every renewal, since certificates expire with the policy term.
• Track it alongside the certificate so the requirement and the proof live together. A certificate of insurance tracking tool stores the certificate and its endorsements with the coverage, limits, and dates, and flags when any of it lapses, so an additional insured gap becomes an alert instead of a surprise. Across a whole vendor list, that is the job vendor insurance compliance software does automatically.

Frequently asked questions

Is the additional insured box on the certificate enough? No. That box is informational. The actual coverage comes from the endorsement attached to the policy, so you need the endorsement form, not just the certificate.

What is the difference between additional insured and certificate holder? A certificate holder simply receives proof of insurance. An additional insured is actually covered by the policy. You usually want to be both, but only additional insured status protects you, and our full comparison of additional insured vs certificate holder works through what each one gets you in a claim.

What is a blanket additional insured endorsement? A form that grants additional insured status to any party the policyholder is required by written contract to add, instead of naming each one. It is convenient, but you still need to confirm the form exists and its wording matches your contract.

Do leases require additional insured status too? Almost always. Commercial leases typically require the tenant to name the landlord as additional insured, which is why the lease's insurance terms and the tenant's endorsement should be tracked together.

Put it together

An additional insured endorsement is what turns a vendor's policy into protection for you, and a certificate checkbox is not proof that it exists. Require it in the contract, collect the actual endorsement form, confirm it names you and is current, and track it with the certificate so a lapse surfaces as an alert. That is the difference between assuming you are covered and knowing it.