A general contractor sends you a subcontract. It requires you to add them as an additional insured on your general liability policy. You call your broker, who says "we've got a blanket AI endorsement — you're covered." The GC's project manager looks at the certificate and asks why your endorsement says "as required by written contract" but their legal name isn't listed. Work stops while your broker scrambles to issue a corrected certificate.
That scenario plays out on Texas job sites regularly. It usually traces back to the same misunderstanding: blanket and scheduled additional insured endorsements work differently, and the contract language has to match the endorsement your policy contains. Getting this wrong doesn't just create paperwork headaches. It can mean a claim gets denied because the coverage you thought you provided wasn't actually in place.
Here's how the two endorsement types work, what they cost, and how to match them to what your contracts actually require.
How Additional Insured Status Works
When a contractor or business is added as an additional insured on your general liability policy, they gain the ability to make claims under your policy for liability arising from your operations. This is different from being a certificate holder — a certificate holder is simply notified if your policy cancels. An additional insured has actual coverage rights.
This matters most when something goes wrong on a job. If a sub causes property damage or a bodily injury, the project owner or general contractor may be named in the lawsuit because they directed the work or own the property. Without additional insured status on the sub's policy, the GC's own insurance has to respond. With it, the sub's policy responds first (assuming primary and noncontributory language is in place), protecting the GC's own limits and loss history.
The additional insured endorsement is the mechanism that grants this status. There are two main types: blanket and scheduled. They differ in how they determine who qualifies as an additional insured.
Scheduled Additional Insured Endorsements
A scheduled additional insured endorsement names specific parties on the policy. Each additional insured is listed by name — "ABC General Contractors, LLC" — and the endorsement specifies the project, location, or scope of coverage for that party.
The most commonly used ISO form is CG 20 10 (for ongoing operations) and CG 20 37 (for completed operations). CG 20 10 covers claims that arise while your work is in progress. CG 20 37 extends protection for claims that arise after the job is finished — the completed operations tail that many contracts require for one to three years after project completion. Most GC contracts require both, and most insurers issue them together as a pair.
When scheduling makes sense
Scheduled endorsements make sense when you have a small number of regular clients who require AI status, or when a project owner or institutional client requires their specific legal entity name to appear on the endorsement. Large municipalities, hospital systems, and some industrial owners verify endorsements against their internal records and will not accept a blanket endorsement because they can't confirm coverage without the scheduled name.
The drawback is administrative: every time you add a new GC or project owner, your broker needs to issue an endorsement. If you're a subcontractor working across multiple job sites with different GCs each month, manually scheduling every one becomes a bottleneck.
Blanket Additional Insured Endorsements
A blanket additional insured endorsement automatically extends additional insured status to anyone your contract requires — without listing them by name on the policy. The most common trigger is the phrase "as required by written contract." When your policy includes a blanket AI endorsement, anyone you've signed a written contract with that requires AI status is automatically covered, up to whatever conditions the endorsement specifies.
The ISO CG 20 33 endorsement is the most widely used blanket form. Some carriers use proprietary language that provides broader or narrower coverage. Read the actual endorsement, not just the summary.
The "written contract" requirement is literal
This is where blanket endorsements most commonly fail at claim time: the coverage only activates if there is a written contract between you and the additional insured that requires them to be added. A verbal agreement doesn't count. An email chain that isn't formalized into a signed contract doesn't count. A certificate that lists someone as additional insured without an underlying written contract doesn't change your policy and doesn't create coverage.
If a claim arises and the carrier asks to see the written contract that triggered the blanket endorsement — and you can't produce one — the AI status may not hold. Document every additional insured relationship with a signed written contract before work begins.
The most dangerous sentence in insurance: "We'll just put them on the certificate." Adding a party as additional insured on the certificate does not change your policy. The certificate is a summary document. Coverage requires an endorsement. If the endorsement isn't there — either by blanket trigger or scheduled name — the certificate statement is inaccurate and the additional insured has no actual coverage under your policy.
Side-by-Side Comparison
| Feature | Blanket (CG 20 33) | Scheduled (CG 20 10 / CG 20 37) |
|---|---|---|
| Who it covers | Anyone required by written contract | Named parties listed on the endorsement |
| Trigger | Written contract requiring AI status | Being listed by name on the endorsement |
| Administrative burden | Low — no per-job requests required | High — each party requires a separate endorsement |
| Typical additional cost | Flat charge or percentage of GL premium — varies by carrier | Per-party charge — varies by carrier and scope |
| Ongoing vs. completed ops | Depends on endorsement language; may cover both or require separate CG 20 37 equivalent | CG 20 10 (ongoing) + CG 20 37 (completed) issued together for full coverage |
| When it fails | No written contract; contract predates the endorsement; endorsement exclusions | Wrong entity name listed; entity name changes mid-project |
The Form Version Problem
ISO has revised these endorsement forms over the years, and the version your carrier uses matters. The CG 20 10 has been updated several times — the 2013 revision narrowed the scope of AI coverage compared to the 2004 version. Some GC contracts specify which version of CG 20 10 they require. If your policy uses the 2013 revision and the contract requires the 2004, there's a mismatch that your broker needs to address with the carrier.
When a GC or project owner has specific form requirements, pull the actual endorsement from your policy — not just the form number — and compare it to what the contract specifies. Gaps between versions become coverage gaps at claim time.
Completed Operations: The Tail Coverage Most Subs Forget
Ongoing operations coverage protects the additional insured for claims that arise while your work is in progress. Completed operations coverage extends that protection for claims arising after the project ends — a structural defect discovered two years later, a water intrusion claim traced back to your work six months after completion.
Many subcontractor agreements in Texas require completed operations coverage for the additional insured for two to five years after project completion. This is particularly common for commercial construction, multifamily projects, and any work on structures where latent defects are a realistic exposure.
When your policy is blanket AI, confirm whether the blanket endorsement covers completed operations or whether you need a separate endorsement. Many blanket AI endorsements (including ISO CG 20 33) cover ongoing operations only. Completed operations coverage for additional insureds often requires a separate endorsement — some carriers issue CG 20 37 equivalents as a standalone add-on, others bundle it into the blanket form. If you're not sure, ask your broker to pull the actual endorsement language and confirm completed ops coverage is included.
What Carriers Offer Blanket Endorsements
Most standard commercial GL carriers offer blanket AI endorsements. Availability narrows in harder-to-place classes — roofing, demolition, crane work — where some carriers only offer scheduled endorsements or exclude AI entirely for certain project types. If your work falls into a high-hazard category, confirm AI endorsement availability when you're shopping coverage, not after you've bound.
Some carriers offer "super blanket" endorsements that combine AI, primary and noncontributory, and waiver of subrogation into a single endorsement triggered by written contract. These simplify certificate issuance significantly and are worth asking about if you're a subcontractor managing a high volume of GC relationships.
Matching the Contract to the Endorsement
The most practical way to prevent AI problems is to work through contract language before you sign. Key questions to ask:
- Does the contract specify scheduled or blanket AI? Most don't — they say "additional insured" without specifying the endorsement type. Blanket usually satisfies this.
- Does the contract require a specific form number? Some sophisticated buyers specify CG 20 10 and CG 20 37 by version. Confirm your policy has them.
- Does the contract require completed operations coverage? If so, confirm your blanket or scheduled endorsement covers it — and for how long.
- Does the contract require primary and noncontributory language? This is separate from AI status and requires its own endorsement (see our guide to additional insured vs. certificate holder).
- What entity name should appear? If you're scheduling by name, the legal entity name must be exact. "ABC Construction" and "ABC Construction, LLC" are different entities.
Cost Comparison
Cost varies significantly by carrier, class of business, and endorsement scope. General patterns:
- Blanket AI: Typically a flat charge or a percentage of GL premium — varies by carrier and program; often included as a standard feature on commercial construction GL policies from carriers focused on contractor business. The charge is not per-relationship, which makes it economical for contractors who add multiple GCs per year.
- Scheduled AI: Usually a per-party or per-project charge. Lower upfront cost if you only add one or two parties per year, but adds up quickly for contractors with many GC relationships.
- Completed operations extension: Usually a separate charge from ongoing ops, regardless of endorsement type. The cost varies by trade and project type — trades with higher completed-ops exposure (structural, mechanical, roofing) pay more.
For most contractors who work with multiple GCs across multiple job sites, blanket AI is more economical and operationally simpler. If you're working exclusively with one or two regular clients, scheduled may cost less. Your broker should be able to quote both.
What to Ask Your Broker
- "Does my policy have a blanket AI endorsement or only scheduled?"
- "What ISO form is it — CG 20 33 or a proprietary endorsement? Can you pull the actual language?"
- "Does the blanket endorsement cover completed operations, or is that a separate endorsement?"
- "If the contract specifies a particular form version of CG 20 10 or 20 37, does my carrier have it?"
- "What written contract documentation do I need to maintain to support blanket AI at claim time?"
Getting Your Certificate Right
Once you have the right endorsements, the certificate needs to reflect them accurately. On the ACORD 25, the "Description of Operations" box is where additional insured language, primary and noncontributory language, and waiver of subrogation are noted. These should reference the actual endorsement forms — not just a general statement that the party is additional insured.
If a GC's project manager or risk department rejects a certificate, the most common reasons are: wrong entity name, missing form numbers, no completed operations language, or a description box that doesn't match what the contract requires. We issue certificates on a published 15-minute SLA and verify endorsement language before sending — catching these issues before they stop a job rather than after. For a full walkthrough of what every certificate field means, see our Certificate of Insurance Guide. If you need a certificate now, see how to get a COI fast.
Frequently Asked Questions
Can I add someone as additional insured after work has already started?
Yes, but the endorsement effective date matters. If a claim arises from work performed before the endorsement was added, coverage may not apply. For ongoing projects, get AI status in place before mobilization — not at first billing.
If I have blanket AI, do I still need to notify my broker when I add a new GC?
No — that's the operational advantage of blanket. The endorsement automatically covers whoever your written contracts require, without per-relationship notifications. You still need to document the written contract to support the coverage at claim time.
What's the difference between CG 20 10 and CG 20 33?
CG 20 10 is a scheduled endorsement that names specific parties and covers ongoing operations. CG 20 33 is a blanket endorsement that covers anyone required by written contract. Pair either with CG 20 37 (or an equivalent) for completed operations coverage.
My carrier uses a proprietary AI endorsement, not an ISO form. Is that a problem?
It depends on the endorsement language. Proprietary forms can be broader or narrower than ISO. Some GC contracts specify ISO forms and won't accept proprietary substitutes. Have your broker pull the actual endorsement and compare it to the contract requirement. If there's a mismatch, you may need to either negotiate with the GC or find a carrier that uses the required ISO form.
For more on the full picture of what additional insured status means — including how it differs from simply being listed as a certificate holder — see our guide to additional insured vs. certificate holder. If your contracts also require primary and noncontributory language, those are two separate endorsements — read our subcontractor insurance requirements in Texas guide for the full stack.