When a general contractor requires a subcontractor to name them as an Additional Insured, the most commonly referenced endorsement is the CG 20 10 10 01. This article explains what that form does, which forms the industry generally treats as equivalent, and what does not meet the standard.
General industry reference only — not legal advice. The insured and their broker are responsible for confirming whether a specific endorsement satisfies their contract requirements.
What is the CG 20 10 10 01?
When a GC hires a subcontractor, the GC usually requires the sub to add them to the sub's liability policy. That's done through an endorsement — a document that modifies the policy to extend coverage to the GC.
The CG 20 10 10 01 is the most widely used standard form for this. It's published by ISO (Insurance Services Office), the baseline language most carriers build from, which is why most GC contracts reference it by name.
The form:
Adds the GC or owner to the sub's policy as a covered party while work is ongoing
Ties that coverage to a written contract between the parties
Is recognized by claims professionals, risk managers, and attorneys across the industry
Important: the CG 20 10 only covers claims arising while work is in progress. A companion form, the CG 20 37, is needed for claims that surface after the project is complete. Many contracts require both.
Form comparison at a glance
Form / Type | What it covers | Industry status | Notes |
CG 20 10 10 01 | Work in progress | Gold standard | Most widely recognized form. Everything else is compared against it. |
CG 20 10 07 04 or 04 13 | Work in progress | Generally accepted | Different wording in newer editions, same purpose. |
CG 20 37 10 01 | After the job is done | Required separately | Completed-operations companion form. Often required alongside the CG 20 10. |
Carrier blanket endorsement | Varies | Conditionally accepted | Reviewed case-by-case against the criteria below. |
CG 20 26 | Named party only | Not equivalent | Adds an additional insured but isn't tied to the work performed. |
Certificate language only | None | Never sufficient | A summary document; not part of the policy. |
Contract language only | None | Never sufficient | A contract can't change what a policy covers. The policy must be endorsed. |
When an insurance carrier uses its own form
Many carriers publish their own proprietary or manuscript endorsement instead of the ISO form. These can be acceptable, but aren't automatically equivalent just because the title is similar. Read the actual wording. The five things reviewers check:
Triggered by a written contract — not just because someone asked. Vague language like "as required" with no written-contract reference is a red flag.
Covers work in progress — liability arising while the sub is actively performing work. This is the core of the CG 20 10.
Covers completed work (if required) — a separate endorsement equivalent to the CG 20 37 must be present.
Pays before the other party's insurance — "primary and non-contributory," often a separate clause.
Does not limit coverage to one-sided fault — coverage should respond even when fault is shared.
Common carrier forms the industry recognizes
Carrier | Common form numbers | Notes |
Zurich | U-GL-1175-A CW, U-GL-2160-A | Blanket forms widely used in construction. |
Travelers | CG D2 46 08 05, CG D3 82 | Separate forms for ongoing and completed operations. |
Liberty Mutual | Varies by program | Blanket forms generally available; confirm written-contract trigger. |
CNA | Varies | Blanket forms generally available; watch for sole-negligence limits. |
The Hartford | HA 99 16 and others | Blanket form; often includes primary and non-contributory language. |
Chubb / ACE | Proprietary blanket forms | Generally strong; confirm completed-operations coverage separately. |
What does not meet the standard
A certificate of insurance listing someone as additional insured — a summary document only; grants no coverage.
Contract language stating the sub will name the GC — a contract can't change policy coverage.
The CG 20 26 form — adds a party but isn't tied to the work performed.
Sole-fault endorsements that only respond when the sub is entirely at fault.
Certificate-triggered endorsements that activate only because a certificate names someone, rather than a written contract.
Quick reference
CG 20 10 = work in progress. CG 20 37 = after completion. Many contracts require both.
Carrier proprietary forms are fine if the language covers the same ground.
Read the endorsement text, not just the form number or title.
A certificate and contract language alone are never sufficient — the policy must be endorsed.
Sole-fault coverage does not meet the standard.
Billy's AI Review Assistant reads endorsement language against your requirements automatically and flags the gaps. Learn more about construction insurance compliance or book a demo.
Last updated: June 2026. General industry reference information only — not legal advice.