In construction, few documents cause more confusion than certificates of insurance and insurance endorsements. Many teams treat them as the same thing. They aren’t, and mixing them up can leave a general contractor completely exposed when a claim comes in.
The short answer: a COI is a one-page summary that shows a policy existed on the day it was issued. An endorsement is part of the policy itself. It’s the endorsement, not the COI, that adds you as an additional insured, waives subrogation or makes the sub’s coverage primary. If the endorsement isn’t attached to the policy, the COI doesn’t protect you.
We talk to contractors every day who received a COI from a subcontractor and assumed they were covered. But a COI only shows that a policy exists. It doesn’t guarantee the GC has any protection under that policy. The protection comes from endorsements, and without them the COI is close to meaningless.
This is one of the biggest blind spots in construction risk transfer today.
COI vs. Endorsement: Side by Side
| Certificate of insurance (COI) | Endorsement | |
|---|---|---|
| What it is | A summary of coverage, usually on an ACORD 25 form | An amendment that is part of the insurance policy |
| Who issues it | The insured’s broker or agent | The insurance carrier |
| Legally binding? | No. It’s informational only. | Yes. It changes the policy contract. |
| Can it add you as additional insured? | No. It can only say an endorsement exists. | Yes. That’s how AI status is granted. |
| What the carrier reads in a claim | Not relied on | The policy and its endorsements |
| What to collect from subs | Yes, as a starting point | Yes, the actual endorsement pages |
What a COI Actually Does
A certificate of insurance is proof that a subcontractor had insurance on the date the ACORD 25 was created. It lists coverage types, limits, effective dates and carrier details. It helps confirm that policies exist, and that’s where its value ends.
A COI isn’t legally binding. It doesn’t amend the policy, transfer risk or give you the rights of an insured. When a claim happens, the carrier doesn’t use the COI to decide whether you’re covered. It looks at the endorsements attached to the policy.
New to COIs? Start with what a COI is in construction and how to read one.
“Many contractors understand this, but fail to operationalise the process, which is why so many claims end up denied.” Sarah Shepard McGuinness
What an Endorsement Actually Does
An endorsement adds to, removes from or changes an insurance policy. It’s the language that decides who is covered, how the coverage applies, when it applies and what’s excluded. It’s the part of the policy that actually decides how a claim turns out.
If a general contractor wants to be an additional insured, that happens through an endorsement. The same goes for a waiver of subrogation and primary and non-contributory wording. Protection during ongoing operations and after the work is complete also comes from endorsements.
That’s why endorsements matter far more than the COI. They are the actual mechanism of risk transfer.
What an Endorsement Page Looks Like
An endorsement page is a separate page attached to the policy. Most construction endorsements are standard ISO forms, so they follow the same layout. When a sub sends you one, check these parts:
- Form number and edition date, usually in the footer, such as “CG 20 10 04 13.” This tells you exactly which version of the coverage you’re getting.
- Title, such as “Additional Insured: Owners, Lessees or Contractors, Scheduled Person or Organization.”
- Policy number and named insured, which should match the sub’s COI.
- Schedule, which lists the additional insured by name (scheduled) or says “any person or organization you are required by written contract to add” (blanket).
- Coverage wording, which spells out what’s covered, such as ongoing or completed operations, and any limits on it.
Red flag: a COI that says “additional insured” or “waiver of subrogation applies,” with no endorsement attached. Always ask the sub’s broker for the endorsement pages themselves.
The Two Endorsements That Matter Most
Commercial general liability policies can carry many endorsements, but two are essential in construction.
CG 20 10
Covers the additional insured for liability from the sub’s ongoing operations. Think of a security guard at the door while a party is still going. CG 20 10 protects the GC while the sub is actively working. Read the CG 20 10 guide.
CG 20 37
Covers the additional insured after the work is complete. The party is over and everyone has gone home, and then you find damage nobody noticed. CG 20 37 protects you from claims that come up after completion. Read the CG 20 37 guide.
You need both. If either one is missing, you’re exposed. See how they work together in our guide to CG 20 10, CG 20 37 and primary and noncontributory.
Example: a completed operations claim
A roofing sub finishes a job. Five weeks later, the chimney they worked on falls onto the neighbor’s greenhouse. Because the job was already finished, this is property damage from the sub’s completed operations. The neighbor sues the property owner.
The owner was named as an additional insured on the roofer’s policy using the current CG 20 10. That endorsement only covers ongoing operations, so the owner has no coverage under the roofer’s policy for this claim.
To be covered for completed operations, the owner needed a CG 20 37 endorsement as well. Editions of CG 20 10 from 10 01 onward don’t include completed operations.
Why the Difference Matters
A COI confirms that insurance exists. An endorsement decides whether you’re actually covered.
That distinction is the foundation of construction risk management. A contractor who collects COIs without checking endorsements is collecting paper, not protection.
Why Manual Review Fails
Most contractors still review COIs and endorsements by hand. It’s slow, inconsistent and often inaccurate. Every carrier words its endorsements differently. Subs send incomplete packets, outdated forms, or let coverage drop mid-project without telling anyone. No reviewer can keep up with hundreds or thousands of vendor documents across multiple jobs and years.
That’s why GCs managing more than a few dozen subs move to software that reviews endorsements, not just COIs. It’s also why Billy built AI directly into the compliance workflow.
How Billy’s AI Reviews COIs and Endorsements
Billy uses AI models trained specifically on construction insurance documents. It reads COIs and endorsements the way an experienced risk manager would, and it applies the same rules to every document.
Billy automatically checks whether the required endorsements are present, including:
- CG 20 10
- CG 20 37
- CG 24 04
- Primary and non-contributory wording
- Additional insured status
- Waiver of subrogation
- Completed operations wording
- Ongoing operations wording
Billy’s AI Review Assistant checks each document against your project’s insurance requirements and flags anything missing or wrong. You get a clear compliance status without digging through PDFs or emailing carriers.
Automated follow-up with subs and brokers
Most compliance delays come from vendors who forget to send documents or don’t know what’s required. Billy sends each vendor a precise request for what your project needs. They upload straight into Billy, and the AI reviews the documents right away. If an endorsement is missing, the vendor sees it immediately. If a policy expires, Billy follows up automatically. Brokers can upload on their clients’ behalf.
The result is a predictable workflow with far less back and forth on every project.
Why GCs Choose Billy
Billy combines AI extraction, automated endorsement review, subcontractor workflows and integrations with Procore, Autodesk, Sage 300, Sage Intacct, Viewpoint Vista, JD Edwards and other core systems. Together they protect the job, the general contractor and the bottom line.
See Billy review a COI and its endorsements in seconds
Book a demo and bring a real subcontractor COI. We’ll show you what’s missing.
Book a demoFrequently Asked Questions
What is a COI endorsement?
“COI endorsement” usually means an endorsement referenced on a certificate of insurance, such as additional insured or waiver of subrogation. The COI only notes that it exists. The endorsement itself is a separate page attached to the policy, and that page is what gives you the coverage.
What is an endorsement page in insurance?
An endorsement page is a form attached to an insurance policy that changes its coverage. It shows a form number and edition date, the policy number, the named insured, a schedule of who’s covered, and the coverage wording.
Does a COI prove additional insured status?
No. A COI can say you’re an additional insured, but it can’t grant that status. Only an additional insured endorsement attached to the policy does. Ask for the endorsement page to confirm it.
What’s the difference between a certificate holder and an additional insured?
A certificate holder just receives a copy of the COI and gets no coverage. An additional insured is added to the policy through an endorsement and can make a claim under it. Read the full comparison.
Is a COI the same as a declarations page?
No. The declarations page is the first page of the policy itself and lists the insured, policy period, coverages and limits. A COI is a separate summary created by the broker. Neither one shows the endorsements in detail.
