Endorsement

Additional Insured

Q: How much does it cost to add an Additional Insured?

Most carriers add Additional Insured at no extra cost via a blanket AI endorsement (ISO CG 20 33 or equivalent) when required by written contract. Specific named-AI endorsements typically cost $25-$150/year per AI when blanket coverage doesn't apply. AI on Commercial Auto is more expensive (~$50-$200/year). Primary-and-non-contributory status adds 5-15% to the underlying GL premium. Always confirm with your agent — many carriers waive small-business AI fees as a goodwill measure.

Q: What's the difference between Additional Insured and Certificate Holder?

Certificate Holder = notification only. The party gets a COI confirming your coverage exists but has no rights under your policy. Additional Insured = actual coverage extension. The party becomes an insured under your policy for liability arising out of your operations or premises. The two terms are routinely confused on COIs — always verify by asking your carrier to send a copy of the AI endorsement page, not just the COI.

Q: Which Additional Insured form should I use?

The most common ISO forms: CG 20 10 (AI for ongoing operations — used during the work), CG 20 37 (AI for completed operations — used after the work is done; critical for contractors), CG 20 26 (AI by written contract, blanket), CG 20 33 (AI for contractors when required by contract). The 2013 revisions of CG 20 10 and CG 20 37 narrowed scope vs the 2004 forms. Ask your agent which year-edition form your carrier uses — older 2004 forms remain broader. IRMI's Additional Insured reference details each form.

By Jason Wootton · Edited by Justin Marks · Reviewed by Jason Wootton, NPN 7694718 Verify NPN ↗ · See disclosures ↓

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Definition. Additional Insured is a third party (landlord, client, vendor) named on your liability policy as also being covered.

Also known as: AI, Additional Insured Endorsement

Additional Insured (AI) is the most-requested endorsement on small-business General Liability and Commercial Auto policies. It extends YOUR policy's liability coverage to protect a named third party — a landlord, client, prime contractor, vendor, or venue operator — for claims arising out of YOUR operations or premises.

The most-confused distinction in commercial insurance: Additional Insured ≠ Named Insured ≠ Certificate Holder. A Certificate of Insurance (COI) with someone listed as "Certificate Holder" just notifies that party your coverage exists — they get NO actual coverage protection from your policy. An Additional Insured endorsement (ISO forms CG 20 10, CG 20 11, CG 20 26, CG 20 33, CG 20 37) actually extends YOUR coverage to them. The form number matters — some grant ongoing operations only; others include completed operations. See also Additional Insured vs Additional Named Insured for a deeper distinction.

Most GL carriers issue blanket AI endorsements at no additional premium when required by written contract; specific named-AI endorsements typically add $25-$150/year per endorsement. Standard ISO forms grant primary-and-non-contributory status only when the contract specifically requires it; without that language, your AI coverage shares loss with the AI's own policy (contribution). AI is often paired with a Waiver of Subrogation in commercial-lease and subcontractor agreements.

Real-world scenario

Tomás is a hypothetical small-business owner; his scenario illustrates how Additional Insured responds in a typical contract-driven claim. It is not based on a specific real customer, claim, or quote from any carrier.

Tomás, residential remodeling contractor — Brooklyn, NY (hypothetical). 4-person crew, ~$680K annual revenue, $1M/$2M GL policy. Lands a $185K kitchen remodel for a building owner who manages a 12-unit condo. The building's master insurance + condo board both require Tomás to add the building owner AND the condo association as Additional Insured (primary & non-contributory) on his GL using ISO form CG 20 10 + CG 20 37 (covering ongoing operations + completed operations).

Three months into the job, Tomás's apprentice nicks a hidden water line behind a wall. Slow leak goes undetected for 6 days, eventually causing $42,000 in damage to the unit below (hardwood floors, drywall, kitchen cabinets, furniture) AND $18,000 to the unit Tomás was renovating (subfloor + cabinet bases). The downstairs unit owner sues the building owner + condo association + Tomás. The plaintiff's attorney also names two contractors who worked at the building in the prior 6 months under a "negligent maintenance" theory.

Tomás's $1M GL policy responds to: (1) his direct liability for the water-line damage ($60K), (2) defense costs for the building owner as AI ($24K), (3) defense costs for the condo association as AI ($18K). Total carrier payout: $102K within policy limits. The two other contractors named under negligent-maintenance theory are dismissed when the leak is traced to Tomás's job. Critically — because of the "primary & non-contributory" AI endorsement language, the building owner's master policy doesn't contribute to the claim; Tomás's GL pays first. Annual cost of the AI endorsement on Tomás's GL: $0 added premium (most carriers include blanket AI when required by written contract); specific named-AI add-ons cost $25-$150/year per endorsement.

How it affects your premium

Additional Insured endorsements don't carry their own premium — they ride on the underlying policy (typically GL or Commercial Auto). Cost impact depends on form + scope:

Blanket AI endorsements — included at no additional premium when required by written contract with most carriers (Hartford, Travelers, Chubb, Hanover, etc.). Common form: ISO CG 20 33 (blanket AI for contractors when required by contract).
Specific named-AI endorsements — typically $25-$150/year per AI when not covered by a blanket form. Common for non-contractual relationships (mortgagee, secured-party AI on commercial property, joint venture partners).
Primary & non-contributory (P&NC) AI — adds 5-15% to the underlying GL premium when required ON TOP of standard AI. The P&NC language makes YOUR policy primary (no contribution from the AI's own carrier).
AI on Commercial Auto — typical $50-$200/year per endorsement (more expensive than AI on GL because auto exposure is concentrated).
Completed Operations AI — ISO CG 20 37 extends AI status to completed operations (the work is done, you've left the site, but a defect manifests later). Critical for contractors. Adds 10-20% to standard AI cost when added.
Waiver of Subrogation — often combined with AI requests. Standard endorsement, typically no additional premium with blanket forms.
Contract review service — some carriers (Hartford, Travelers) offer free contract review to identify the correct AI form for each contract type; valuable for contractors signing 10+ contracts/year.

Bottom line: AI itself is rarely a meaningful line item on a small-business commercial policy. The premium driver is the underlying coverage — see GL premium factors ($45/mo median per industry-typical 2024).

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Common misconceptions

Myth: Listing someone as Certificate Holder gives them coverage under my policy.

Reality: No — Certificate Holder gives them ZERO coverage. A Certificate of Insurance with a Certificate Holder listed just NOTIFIES that party your coverage exists; it does NOT extend coverage to them. To actually grant coverage, you need an Additional Insured endorsement issued by your carrier (ISO forms CG 20 10, CG 20 26, CG 20 37, etc.). This is the #1 source of confusion at COI delivery time and the #1 source of post-claim disputes between landlords/GCs and tenants/subs.

Myth: Adding an Additional Insured is automatic — I just write their name on the COI.

Reality: The COI is just a one-page summary. The actual AI grant comes from the endorsement attached to your policy (issued by your carrier on a specific ISO form). Without the underlying endorsement on file with your insurer, the COI's AI line is meaningless — the carrier will deny AI status at claim time. Always confirm AI is on the policy (request a copy of the endorsement page) before the COI ships.

Myth: Additional Insured covers the AI for everything they're sued for.

Reality: AI coverage is limited to liability arising out of YOUR operations or premises — not the AI's own negligence or activities. If a landlord-AI is sued for their OWN negligent maintenance (unrelated to your tenancy), your policy won't respond. The 2013 ISO form revisions (CG 20 10 13, CG 20 37 13) narrowed AI coverage further by adding sole-negligence-of-AI exclusions. Read the actual endorsement form to understand the scope.

Frequently asked questions

How much does it cost to add an Additional Insured?

Most carriers add Additional Insured at no extra cost via a blanket AI endorsement (ISO CG 20 33 or equivalent) when required by written contract. Specific named-AI endorsements typically cost $25-$150/year per AI when blanket coverage doesn't apply. AI on Commercial Auto is more expensive (~$50-$200/year). Primary-and-non-contributory status adds 5-15% to the underlying GL premium. Always confirm with your agent — many carriers waive small-business AI fees as a goodwill measure.

What's the difference between Additional Insured and Certificate Holder?

Certificate Holder = notification only. The party gets a COI confirming your coverage exists but has no rights under your policy. Additional Insured = actual coverage extension. The party becomes an insured under your policy for liability arising out of your operations or premises. The two terms are routinely confused on COIs — always verify by asking your carrier to send a copy of the AI endorsement page, not just the COI.

When do I need primary-and-non-contributory Additional Insured?

When the underlying contract requires it (most subcontractor agreements with major GCs do). Primary-and-non-contributory (P&NC) language makes YOUR policy pay first AND prevents your carrier from seeking contribution from the AI's own policy. Without P&NC, both policies share loss pro-rata, which can leave the AI's own deductible exposed. Standard ISO additional-insured endorsements are NOT automatically P&NC — you need the specific P&NC language attached. Adds ~5-15% to the underlying GL premium.

Which Additional Insured form should I use?

The most common ISO forms: CG 20 10 (AI for ongoing operations — used during the work), CG 20 37 (AI for completed operations — used after the work is done; critical for contractors), CG 20 26 (AI by written contract, blanket), CG 20 33 (AI for contractors when required by contract). The 2013 revisions of CG 20 10 and CG 20 37 narrowed scope vs the 2004 forms. Ask your agent which year-edition form your carrier uses — older 2004 forms remain broader. IRMI's Additional Insured reference details each form.

Sources cited

Additional Insured (AI) — International Risk Management Institute (IRMI) (2024)
Certificate of Insurance — Definition — International Risk Management Institute (IRMI) (2024)
Insurance for Your Business — Insurance Information Institute (III) (2024)

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Disclosures

📘 Educational content only. Reviewed by licensed Property & Casualty insurance agent Jason Wootton (NPN 7694718). Not insurance advice, an individual recommendation, or a solicitation in any state. Insurance regulations vary by state. For specific coverage decisions, consult a licensed insurance agent in your state.

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