ISO Additional Insured Forms Explained: CG 20 10, CG 20 26, CG 20 37, and More

A general contractor handed you a contract that says "you must add us as an additional insured using ISO form CG 20 10 for ongoing operations and CG 20 37 for completed operations." You stare at the page. What are these numbers? Why two of them? Are they the same as the blanket endorsement your agent mentioned? This guide decodes every additional insured form you're likely to see on a Washington construction or commercial contract — what each one does, when it's used, and which ones you should actually have on your policy.

Quick Form Reference

| ISO Form | What It Does | Named or Blanket | Operations Covered | |---|---|---|---| | CG 20 10 | Adds a specific party as AI | Named (scheduled) | Ongoing operations only | | CG 20 11 | Adds a specific party as AI for completed ops | Named (scheduled) | Completed operations | | CG 20 26 | Adds AI for designated person/organization | Named (scheduled) | Both ongoing + completed (broad) | | CG 20 33 | AI for any organization required by contract | Blanket | Ongoing operations only | | CG 20 37 | Adds a specific party for completed ops | Named (scheduled) | Completed operations only | | CG 20 38 | AI for any organization required by contract | Blanket | Ongoing + completed |

If your contract requires both ongoing AND completed operations coverage (most do), you need CG 20 38 (blanket) or the combination of CG 20 33 + CG 20 37 (named/blanket mix). Many contractors think one form covers everything — it doesn't.

Get a quote with the right endorsements built in → · Chat with Dani · Call 425-209-1206

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Why So Many Forms?

ISO (the Insurance Services Office) writes the standard endorsement forms most US insurers use. When a GC's contract requires you to add them as an additional insured, the contract often references a specific ISO form by number. That's because not all AI forms cover the same things — and the GC wants to make sure they're protected for the specific type of claim they're worried about.

Three things vary across these forms:

1. Who is covered — a specifically named party, or "any organization required by written contract" (blanket) 2. What operations are covered — ongoing work, completed work, or both 3. Trigger language — when the coverage activates (signed contract, work performed, etc.)

A contract that just says "add us as additional insured" is ambiguous. A contract that says "add us using CG 20 10 for ongoing operations and CG 20 37 for completed operations" is specific — and that specificity matters when a claim hits.

The Six Forms You'll Actually See

CG 20 10 — Additional Insured Owners, Lessees, or Contractors (Scheduled, Ongoing Only)

The most commonly requested AI form. CG 20 10 names a specific party — by exact legal name and address — as an additional insured for ongoing operations only. That means it covers claims arising from work as it's being performed, but does NOT cover claims from completed work after you've left the site.

When it's required: A GC, property owner, or project manager wants direct AI status for the duration of your work. Common in residential construction, smaller commercial jobs, and one-off engagements where the relationship ends when the project does.

The catch: CG 20 10 does NOT cover completed operations. If the GC has a claim from your work after you finish (a railing fails six months later), this form alone won't cover them. They'd also need CG 20 37 or CG 20 11 for completed ops.

Edition dates matter: There are multiple editions of CG 20 10 (07 04, 04 13, etc.). Newer editions are generally narrower — they require a written contract as a trigger, where older editions did not. If a contract specifies an edition date, your endorsement must match.

CG 20 11 — Additional Insured Managers or Lessors of Premises

Names a specific landlord, building manager, or premises owner as an AI for liability arising from your operations on their premises. Most often required when you're a tenant or you're doing work inside someone else's building.

When it's required: Lease agreements where the landlord wants AI status. Also common in property management contracts.

Different from CG 20 10: CG 20 11 specifically applies to premises ownership/management exposure, not generic project AI. If you're doing work on a leased property, the building owner often wants CG 20 11 to protect them for liability arising on their premises.

CG 20 26 — Additional Insured Designated Person or Organization (Broad)

Names a specific party and provides AI coverage for both ongoing AND completed operations — broader than CG 20 10 alone. Less common than CG 20 10 + CG 20 37 because most carriers prefer the two-form approach for control over completed-ops exposure.

When it's required: Sophisticated commercial contracts where the requesting party wants single-form, broader coverage.

CG 20 33 — Additional Insured Owners, Lessees, or Contractors (Blanket, Ongoing Only)

The blanket version of CG 20 10. Provides AI coverage to any person or organization you're required to add by written contract — but only for ongoing operations. No need to schedule individual parties; the coverage is automatic the moment a qualifying contract is signed.

When it's required: Used as a default endorsement on most contractor GL policies. Eliminates the administrative burden of adding scheduled endorsements for every new GC or client.

The catch: Like CG 20 10, this form covers ongoing operations only. To get blanket coverage for completed ops, you also need CG 20 38 or the older two-form blanket combination.

CG 20 37 — Additional Insured Owners, Lessees, or Contractors (Scheduled, Completed Operations)

The completed-operations companion to CG 20 10. Names a specific party as AI for completed operations only — meaning claims that arise after your work is finished and you've left the site.

When it's required: Almost always paired with CG 20 10 in construction contracts. Together they give the named party full AI coverage for both phases of your work.

Why it matters in WA: Washington's statute of limitations for construction defect claims can extend years after project completion. CG 20 37 is what protects a GC if a claim hits two or three years after you finished the job.

CG 20 38 — Additional Insured Owners, Lessees, or Contractors (Blanket, Both Operations)

The form most contractors actually want. CG 20 38 provides blanket AI coverage for both ongoing AND completed operations to any party you're required to add by written contract. One form, full coverage, automatic activation.

Why it's the winner: No scheduling. No per-project endorsement requests. Covers both phases of work. Most GCs and property owners accept blanket language.

Why your policy might not have it: Some carriers issue CG 20 33 (blanket ongoing) but not CG 20 38 (blanket both). If your policy only has the ongoing-only blanket, you've got a gap on completed operations. Worth checking.

How to Read a GC's Insurance Requirement

Most contracts list the forms they require. Examples:

> "Subcontractor shall add Owner and General Contractor as Additional Insureds using ISO Form CG 20 10 (Edition 07 04 or later) for ongoing operations and ISO Form CG 20 37 (Edition 07 04 or later) for completed operations."

This is unambiguous. You need both forms, edition 07 04 or newer, naming both the Owner and GC.

> "Additional insured status shall be provided on a primary and non-contributory basis."

This is layered on top of the AI requirement. Your AI endorsement also needs to be primary (pays before any other policy) and non-contributory (your insurer doesn't share the loss with the AI's insurer). See our waiver of subrogation and primary/non-contributory guide for the full breakdown.

> "Contractor shall provide blanket additional insured coverage to all upstream parties required by the construction contract, including but not limited to ongoing and completed operations."

This is asking for CG 20 38 (or the equivalent CG 20 33 + CG 20 37 blanket combination, which is rarer).

If a contract is vague — just says "add us as additional insured" — ask for clarification or default to providing blanket coverage for both ongoing and completed operations (CG 20 38). It's the safest choice and rarely rejected.

> Stuck on a contract? Read us the AI clause and we'll tell you what your policy needs. Call 425-209-1206 or start a quote and we'll set up coverage that meets the requirement.

What Most WA Contractors Should Have on Their Policy

For working contractors handling 5+ contracts per year, the recommended policy structure is:

• CG 20 38 (blanket AI for ongoing + completed operations) — covers nearly every contract requirement
• Blanket waiver of subrogation — required by most institutional clients
• Blanket primary and non-contributory — required alongside AI on most large contracts
• CG 20 11 added when needed for a specific landlord or premises lessor

This setup handles 90% of incoming contract requirements without per-project endorsement requests, processing delays, or per-endorsement fees.

Contractors who only do a handful of jobs per year, or who only work with a single GC, may be fine with scheduled CG 20 10 + CG 20 37 endorsements naming that one party. But the moment you start handling multiple GCs or commercial contracts, blanket coverage saves significant time, money, and risk.

Frequently Asked Questions

What's the difference between CG 20 10 and CG 20 37? CG 20 10 covers ongoing operations (claims while work is being performed); CG 20 37 covers completed operations (claims after work is finished). Most construction contracts require both. They're commonly paired.

Is CG 20 38 the same as "blanket additional insured"? Yes — CG 20 38 is the most common ISO form that provides blanket additional insured coverage for both ongoing and completed operations. Some carriers use proprietary forms with similar language; the result is the same.

My contract requires "CG 20 10 11 85" — what's the 11 85? Those are edition dates. CG 20 10 11 85 is the November 1985 edition. Older editions are typically broader than newer ones (the 1985 edition didn't require a written contract as a trigger). Many carriers no longer issue this old edition. If a contract specifies an edition you can't get, you may need to negotiate the requirement or use a newer-edition equivalent.

What if my carrier uses a proprietary form instead of CG 20 38? Most carriers have their own version of blanket AI that mirrors CG 20 38's coverage. The form number will be different, but the effect is the same. Your COI will list the form number used. If a GC specifically demands an ISO-form CG 20 38 and your policy only has a proprietary equivalent, that can be a sticking point — work with your agent to either negotiate the requirement or get a CG 20 38 issued.

Can I get same-day blanket additional insured coverage? Yes. Most contractor GL policies bind same-day, and SmartInsured sets up blanket AI as standard. You can have a Certificate of Insurance with the right AI language in your hands within an hour of binding.

Does my General Liability policy automatically include these endorsements? Some policies do; some don't. Standard "off-the-shelf" GL policies often include CG 20 33 (blanket, ongoing only) but not the completed-operations companion. You typically need to specifically request CG 20 38 or a broader blanket form. Read your policy or ask your agent.

Is there an AI form for commercial auto policies? Yes — separate ISO forms apply to commercial auto AI requirements (e.g., CA 20 48). They work similarly but apply to your commercial auto policy, not your GL. If a contract requires AI on both your GL and your auto, you need both forms.

Three Ways to Get the Right Endorsements

If you have a contract that requires specific ISO forms — or if you're not sure whether your current policy actually has the forms a GC is asking for:

1. Start a quote (4 minutes) — we'll set up CG 20 38 + waiver + P&NC as standard for WA contractors 2. Chat with Dani if you'd rather talk through it conversationally 3. Call 425-209-1206 if you need to read us a contract clause directly — we'll tell you exactly what your policy needs

Same-day binding and certificates of insurance available for Washington contractors. Don't let an endorsement requirement cost you a job.