An insurance endorsement is a formal amendment to a policy that adds, restricts, or clarifies coverage. It is the instrument that actually changes what the policy insures. The certificate of insurance references endorsements the broker or agent believes are attached, and it is the endorsement itself, on the policy behind the certificate, that decides whether coverage responds to a third party.

Endorsements range from routine administrative changes, such as adding a location or adjusting a limit, to the ones that decide whether a policy responds to someone other than the policyholder. This guide explains what an endorsement is, then concentrates on the group that carries contractual risk transfer in construction and vendor programs: CG 20 10 and CG 20 37 for additional insured status, CG 24 04 for waiver of subrogation, and CG 20 01 for primary and noncontributory.

What is an insurance endorsement?

An endorsement is a written amendment to an insurance policy. It is issued by the insurer, attached to the policy, and it changes what the policy covers, whom it covers, or how it responds. Endorsements can add coverage (adding an additional insured), restrict coverage (removing an exposure), or clarify how the policy behaves (specifying the order of payment when other insurance applies).

Two kinds of endorsement matter in this guide. Standard forms are drafted by the Insurance Services Office (ISO) and used by most commercial general liability insurers. They are identified by codes such as CG 20 10 or CG 24 04. Manuscript endorsements are custom, drafted for a specific policy. Both are amendments to the policy in the same legal sense; the difference is how consistent they are across carriers.

The four endorsements this guide focuses on are standard ISO forms. Together they carry the mechanics of contractual risk transfer at the certificate and endorsement level. The certificate of insurance can reference all four and describe them accurately, and each of them can still be missing, narrower than expected, or issued against the wrong entity on the policy itself. The endorsement is what matters. The certificate is a description of the endorsement's intent, not the endorsement.

Why does the ACORD 25 tell you to confirm the endorsement?

Because ACORD says so on the certificate itself. Below its disclaimer, the ACORD 25 carries a notice that if the certificate holder is an additional insured, the policy must have additional insured provisions or be endorsed, that if subrogation is waived, an endorsement may be required, and that a statement on the certificate does not stand in for either. In ACORD's own words, the certificate "does not confer rights to the certificate holder in lieu of such endorsement(s)." (ACORD 25, 2016/03 edition.)

The word "provisions" in that notice is deliberate. ACORD added it in the 2016/03 edition because many carriers grant additional insured status through blanket provisions built into the coverage form itself, triggered by a written contract, with no separate endorsement attached. The grant still has to exist in the policy. The certificate still cannot create it.

This is not defensive drafting on ACORD's part. The "information only" language conforms the certificate to the Insurance Law, which prohibits an insurer from making a contract of insurance other than as plainly expressed in the policy. (New York DFS Office of General Counsel Opinion 00-09-04.) A certificate cannot create coverage the policy does not contain, as a matter of law.

The practical consequence is precise. Naming a party as additional insured on the certificate, ticking a waiver-of-subrogation box, or asserting primary and noncontributory language in the description of operations does not grant any of those coverages by itself. Each requires an endorsement or a qualifying provision on the policy. The rest of this guide is what those endorsements are and where they fail.

What does CG 20 10 actually cover, and what does it not cover?

CG 20 10, "Additional Insured, Owners, Lessees or Contractors," grants additional insured status for the named insured's ongoing operations only. ISO revised the endorsement in 1993 specifically to rule out completed operations coverage for additional insureds. ISO commented that it was never the insurance industry's intention to give additional insureds completed operations coverage under CG 20 10. (IRMI, Additional Insureds and Completed Operations.)

The scope matters and the wording matters. Ongoing operations is the exposure during the work: the subcontractor is on site, the work is in progress, and something happens. Completed operations is the exposure after the work is finished and the subcontractor has left, when a defect surfaces months or years later. CG 20 10 covers the first. It does not cover the second.

Two consequences follow. First, requiring only CG 20 10 in a subcontract leaves a gap that opens the moment the subcontractor walks off site, because completed operations coverage was never granted. Second, the certificate cannot tell you whether the additional insured endorsement on the policy is a CG 20 10 alone, a CG 20 10 paired with a CG 20 37, or a different endorsement entirely. It references the endorsement; it does not reproduce it.

Why is CG 20 37 a separate endorsement from CG 20 10?

Because ISO chose to make completed operations coverage a separate purchase decision. CG 20 37 restores completed operations coverage as its own endorsement, and it is required whenever a general contractor's exposure extends past project completion, which is nearly always in construction. (IRMI, same.)

The failure mode is worth describing concretely. A subcontractor finishes their scope and the certificate shows additional insured status. Eight months later a defect surfaces. The general contractor tenders the claim under the subcontractor's CG 20 10. The carrier denies it, because CG 20 10 covers only ongoing operations and the work was completed months earlier. The contract never required CG 20 37, so the completed operations exposure was never covered. (IRMI, same.)

That failure passes a certificate check. The certificate references the additional insured endorsement, the box is ticked, and the record looks complete. The gap is inside the policy: only one of the two endorsements needed for a project lifecycle is there. The gap does not surface until the tender.

CG 20 10 and CG 20 37 are a matched pair for construction. Requiring both, and confirming both are on the policy, is what closes the completed-operations gap. Requiring only one leaves an exposure that a certificate cannot see and cannot warn you about.

Do endorsement editions matter?

Yes. Editions of the same endorsement number differ materially, and the certificate does not show which edition is on the policy. If a contract was drafted around the CG 20 37 10 01 edition and the carrier issues the 04 13 or 12 19 edition, the additional insured may have narrower protection than the contract intended, and the edition cannot be changed after a claim arises. (IRMI, Questions and Answers on Additional Insured Issues.)

The mechanism ISO uses tightens the point further. When ISO files a new edition of an endorsement, it withdraws the previous one, so older editions are no longer approved for use in most states and would require a special filing. In practice, this means a contract that specifies an older edition is asking for a form that may no longer be filed for use, and the carrier will usually issue whichever current edition it uses instead, though some carriers maintain independent filings of older editions and will issue them on request. Whether the issued edition matches the contract's intent is a question the certificate does not answer.

Edition detail is one of the reasons certificate-level review is not sufficient for high-exposure work. The certificate lists "CG 20 37" or "CG 20 10" and moves on. Reading the endorsement itself is the only way to see the edition date, and reading it against the contract requirement is the only way to know whether the coverage granted is the coverage the contract asked for.

What does "caused, in whole or in part" actually cover?

This is the wording that decides whether the additional insured coverage responds at all, and it changed materially in 2004.

The 1985 CG 20 10 covered the additional insured for liability "arising out of" the named insured's work, which was broad enough to reach the additional insured's own negligence. The 2004 revision replaced "arising out of" with coverage for injury or damage "caused, in whole or in part, by" the acts or omissions of the named insured or those acting on its behalf. The 04 13 and 12 19 editions carry the same wording forward. (IRMI, 2013 ISO Additional Insured Endorsements.)

The consequence is specific: under a post-2004 form, the additional insured is covered only where the named insured, the subcontractor, actually contributed to the loss. If the loss was caused solely by the additional insured, there is no additional insured coverage, and the additional insured falls back on its own policy.

IRMI's worked examples make the boundary concrete. A subcontractor installs a pipe negligently, it falls and injures a pedestrian, and the general contractor was also partly at fault for not protecting the passer-by. Because the injury was caused in part by the subcontractor, the general contractor is covered as an additional insured. In a second case, the general contractor improperly sets up a scaffold and a worker falls, and the injury is found to be wholly the general contractor's fault. Because the subcontractor did not contribute to the loss, the general contractor has no additional insured coverage and must rely on its own policy. (IRMI, Additional Insured Changes in the CGL.)

A second narrowing arrived with the 04 13 editions, and it links directly to contractual risk transfer. The insurance afforded to the additional insured applies only to the extent permitted by law, and is no broader than what the named insured was required by contract to provide. If the contract required 1 million dollars in limits and the subcontractor carries 2 million dollars, the additional insured gets the benefit of only 1 million dollars. And where a contract's requirement is vague, the coverage granted can be vague with it. Precise contract wording is what fixes the scope of the endorsement.

What does CG 24 04 do?

CG 24 04, titled "Waiver of Transfer of Rights of Recovery Against Others to Us," is the ISO endorsement that adds a waiver of subrogation to a commercial general liability policy. Subrogation is the insurer's right, after paying a claim, to step into the insured's shoes and pursue recovery from a third party at fault. The waiver removes that right, with respect to specifically named upstream parties.

The blanket version is CG 24 53, which waives subrogation automatically as to any party the named insured has agreed in a written contract to waive rights against. Editions of CG 24 04 include the 05 09 and 12 19 versions, and the 2019 revision was meant to clarify certain privity-of-contract ambiguities in the earlier wording. (IRMI, Subrogation and the CGL Policy.)

The mechanics are narrow and important. Where the endorsement applies, the subcontractor's insurer cannot recover from the upstream party after paying the loss on the subcontractor's behalf. That is what the endorsement does. It is not what most people asking for it believe it does, and the misunderstanding is the subject of the next section.

What does CG 24 04 not do?

Three things, and each of them is commonly misunderstood.

CG 24 04 does not create primary and noncontributory coverage. Primary and noncontributory is a separate endorsement, CG 20 01, that changes how the policy shares a loss with other insurance. A waiver of subrogation and primary and noncontributory language are two different endorsements doing two different jobs. Contracts routinely list them together, and both are needed; neither substitutes for the other. (IRMI, same.)

CG 24 04 does not add additional insured status. Additional insured status comes from the CG 20 series of endorsements. A party that is a certificate holder with a waiver of subrogation in its favor is not, by that fact alone, an additional insured. The two are distinct grants, and the waiver operates whether or not the upstream party is also named as an additional insured.

Only the insurer waives. This is the most important of the three misunderstandings. Under CG 24 04, the insurer gives up its right to subrogate against the named upstream party after paying a loss. The named insured, the subcontractor itself, has waived nothing. The subcontractor can still pursue the upstream party directly, for example to recover a large deductible or self-insured retention it had to fund out of pocket. Parties who demand a waiver of subrogation frequently believe it forecloses that. It does not. (IRMI, same.)

One further point on scope. CG 24 04 applies only to persons or organizations identified in the endorsement's schedule, and only for injury or damage arising out of the named insured's ongoing operations or work done under a contract with them. The written contract is what creates the obligation to obtain the waiver; the schedule is what defines who the endorsement actually reaches, and the schedule is what gets verified. It is not a blanket waiver against all third parties. The blanket variant, CG 24 53, waives subrogation as to any party the named insured has agreed in writing to waive rights against, but even that is triggered by a written contract to waive; it is not a waiver in the air.

The practical implication is that a waiver of subrogation is worth requiring in every high-exposure subcontract, and it is worth understanding narrowly. It stops the sub's carrier from coming for the upstream party after the loss. It does not stop the sub from coming, it does not grant additional insured status, and it does not change how the policy shares a loss with the upstream party's own insurance.

Why do contracts also require primary and noncontributory?

Because the priority of coverage only works when both policies say what the contract assumed they would say, and one of them usually is not the contract drafter's to control.

Under standard ISO wording the priority already runs the intended way. The subcontractor's policy is primary for an additional insured, and the upstream party's own ISO policy makes itself excess over coverage available to it as an additional insured. Where every carrier in the chain is on current ISO forms, the sub's policy pays first without any help.

The problem is that the upstream party cannot count on it. Many carriers write additional insured coverage on proprietary endorsements whose other-insurance wording makes the coverage excess unless a written contract requires primary. Older and non-ISO forms in the upstream party's own program may lack the excess-when-additional-insured provision, leaving two primary policies to share the loss. And absent noncontributory wording, the subcontractor's carrier can pay and then seek contribution from the upstream party's carrier, which puts the loss back on the upstream party's history through the side door. (ISO CG 00 01, Other Insurance condition; IRMI.)

CG 20 01 is the endorsement that removes the uncertainty. It makes the subcontractor's policy pay first, before the upstream party's coverage responds, and the insurer agrees not to seek contribution from any other insurance available to the additional insured, where the written contract requires primary and noncontributory coverage. Together, additional insured status plus primary and noncontributory language keeps the loss on the subcontractor's program, where the risk transfer was meant to put it, regardless of whose forms are in play.

The failure mode without CG 20 01 is quiet. The subcontractor has a policy, the general contractor is an additional insured on it, and the claim is tendered. The subcontractor's carrier is on a proprietary endorsement that makes the additional insured coverage excess without contract-required primary wording, or it pays and then pursues contribution from the general contractor's carrier. Either way the general contractor's program absorbs part of a loss the contract moved downstream. The general contractor's loss history takes the hit. The certificate showed a checkbox for primary and noncontributory. The policy did not have the endorsement.

Primary and noncontributory belongs in every subcontract that requires additional insured status. Without it, the coverage that was supposed to move the loss to the subcontractor's program can end up sharing it with the upstream party's program instead.

What about blanket versions like CG 20 33?

CG 20 33 is the automatic, or blanket, additional insured endorsement for ongoing operations. Rather than naming specific parties, it grants additional insured status to any party the named insured has agreed in a written contract to add as an additional insured. It is convenient because it triggers on the existence of a contractual requirement, without requiring a separately scheduled endorsement per upstream party.

The important limit is the one that carries over from CG 20 10. CG 20 33 grants additional insured status for ongoing operations only. It does not grant completed operations coverage. Requiring only CG 20 33 in a subcontract creates the same completed-operations gap as requiring only CG 20 10, because the blanket coverage stops at the same boundary the underlying endorsement does. Full-lifecycle coverage still requires a completed operations endorsement, either CG 20 37 or a comparable form; the automatic completed-operations equivalents are CG 20 39 and, for parties without a direct contract, CG 20 40.

There is also a trap inside the blanket forms that a certificate will never reveal. CG 20 33 grants automatic additional insured status only to a party the named insured has a direct written contract with. On a multi-tier project, that leaves out upstream parties the subcontractor never contracted with directly. An owner two tiers above a sub-subcontractor can be a required additional insured and get no coverage under CG 20 33, because there is no direct contract between them. CG 20 38 is the form that closes this: it extends automatic status to parties the named insured is required by its contract to cover, whether or not the named insured contracted with them directly. On layered construction jobs, requiring CG 20 38 rather than CG 20 33 is often the difference between the owner being covered and not. (IRMI; ISO form comparison.)

The blanket waiver of subrogation, CG 24 53, works the same way as the scheduled version. It waives subrogation against any party the named insured has agreed in writing to waive rights against, which reduces the administrative burden of naming each party. It is still triggered by a written contract to waive, and it still carries the three "does not do" limits in the section above.

Blanket endorsements simplify the paperwork. They do not change the substantive limits of the coverage they grant, and CG 20 33 in particular can grant less than a layered project needs.

How do you verify these endorsements are on the policy?

By reading the endorsement, not the certificate, and by reading it against the contract requirement. The certificate is a summary, and every failure this guide describes is a failure that survives certificate review because the failure is in the policy, not the summary.

At the endorsement level, verification is specific. For each endorsement the contract required, the questions are whether the endorsement or an equivalent policy provision is on the policy, whether it is the correct edition, and whether it names the correct legal entity where an entity is named. For CG 20 10 and CG 20 37, both are required in construction, and the completed operations edition must actually be attached. For CG 24 04, only the insurer's rights are waived; the endorsement should name the upstream party in its schedule or, in a blanket form, be triggered by a written waiver requirement. For CG 20 01, primary and noncontributory language must be in the endorsement on the policy, not just referenced on the certificate.

For high-exposure work, verification moves to the policy as a whole. Coverage-removing endorsements at the policy level, exclusions that apply to the work, and inconsistencies between the additional insured endorsement's scope and the contract's requirements are policy questions that a certificate and endorsement check cannot resolve. That level of review is a Comprehensive Policy Review, and it is the ladder from this guide up into the contractual risk transfer guide.

Docutrax runs endorsement and policy reviews of this kind as a matter of course. Certificates, endorsements, and policies are reviewed by licensed P&C professionals, and construction accounts are handled by CRIS-certified Account Managers, on a base of more than 300,000 complete policy reviews since 2017. Where an endorsement is missing, is the wrong edition, or names the wrong entity, the team coordinates the correction with the subcontractor's broker or agent and surfaces the facts to the client. Docutrax does not decide for the client whether to let a non-compliant subcontractor proceed. It provides the documentation and analysis so the client can decide with the coverage picture in front of them.

Four endorsements, four different jobs. CG 20 10 grants ongoing-operations additional insured coverage. CG 20 37 grants completed-operations coverage. CG 24 04 stops the insurer from subrogating against the upstream party. CG 20 01 makes the coverage pay first. Each is a separate written amendment to the policy. A certificate that references any of them is describing the broker or agent's intent. The policy is telling you whether the endorsement is actually there.