CG 20 01 is the ISO endorsement that makes your general liability coverage primary and noncontributory for an additional insured when a written contract or agreement requires it. It modifies the Other Insurance condition of the CGL policy so your insurer pays a covered loss first and does not ask the additional insured's own insurer to chip in.
Nearly every construction contract that requires additional insured status also contains the phrase primary and noncontributory, and this endorsement is the standard ISO way to honor that promise. This page explains what the words mean, what the endorsement actually changes, and why the phrase on a certificate is worthless without the form behind it.
What does CG 20 01 do?
The unendorsed CGL policy contains an Other Insurance condition in Section IV that decides what happens when more than one policy covers the same loss. When an additional insured is added to your policy, that condition already makes your coverage primary for the additional insured, but the additional insured's own policy may also respond, and two primary policies covering the same loss share it under the methods the condition describes.
An upstream party that negotiated for your insurance does not want its own limits eroded or its loss history touched, so it demands that your coverage be primary and noncontributory. CG 20 01 delivers that by amending the condition so your insurance is primary to, and will not seek contribution from, other insurance available to the additional insured, provided a written contract or agreement requires it.
ISO introduced the endorsement in the 04 13 revision cycle to give the market a standard form answer to a demand that contracts had been making for years.
The endorsement only works on top of existing additional insured status. If the contract requires CG 20 10 and CG 20 37, CG 20 01 is the third piece that controls how the three policies interact after a loss, and our guide to additional insured endorsements shows how the pieces fit together.
What does primary and noncontributory actually mean?
The two words solve two different problems. Primary answers the order-of-payment question, meaning your policy responds to the additional insured's covered loss before its own insurance does. Noncontributory answers the sharing question, meaning your insurer will not later demand that the additional insured's insurer contribute a share of what was paid. Without the second word, your carrier could pay the claim and then pursue the additional insured's carrier for contribution, which drags the upstream party's policy into the loss anyway.
Sharing is not a theoretical concern, because the CGL Other Insurance condition spells out exactly how two primary policies split a loss. If the other insurance permits contribution by equal shares, each insurer pays equal amounts until its limit is exhausted or the loss is paid. If it does not, the policies share pro rata by limits. Here is what a $300,000 covered loss looks like under each method when two primary policies apply:
| Sharing method | Policy A ($500,000 limit) | Policy B ($1,000,000 limit) |
|---|---|---|
| Equal shares | $150,000 | $150,000 |
| Pro rata by limits | $100,000 | $200,000 |
CG 20 01 exists to take the additional insured's policy out of that math entirely. With the endorsement attached and a qualifying written contract in place, your policy absorbs the covered loss up to its limits and the additional insured's insurer pays nothing.
Why do contracts require it?
An owner or general contractor requiring additional insured status is transferring risk downstream to the party performing the work, and the transfer is incomplete if its own policy still shares the loss. Every claim that touches the upstream party's policy affects its loss history and future premiums, which is exactly what the additional insured bargained to avoid.
Requiring primary and noncontributory wording closes the loop, so the subcontractor's insurance stands alone in front of the claim. The requirement appears almost universally alongside additional insured clauses in construction subcontracts, leases, and service agreements, and carriers see it often enough that many build equivalent wording into their blanket additional insured endorsements rather than attaching CG 20 01 separately.
What should you check before agreeing to provide it?
Contract insurance requirements are commitments your policy either can or cannot keep, and the time to find out is before signature. Run through these checks with your broker:
- Confirm the endorsement or its equivalent is on the policy: ask whether your carrier attaches CG 20 01 itself or builds primary and noncontributory wording into its blanket additional insured endorsement, and get the answer in writing.
- Get the written contract signed first: the endorsement applies only when a written contract or agreement requires primary and noncontributory coverage, so an unsigned or after-the-fact agreement leaves the requirement unmet.
- Verify the additional insured forms are in place: cG 20 01 changes payment order for parties who are already insureds. Confirm the contract's CG 20 10 and CG 20 37 requirements are satisfied on the same policy, or the wording has nothing to act on.
- Never rely on certificate language alone: typing primary and noncontributory on a certificate confers nothing. The condition changes only if the endorsement or equivalent policy wording is actually attached, so request the form when you are the party being protected.
Where can you see the actual form?
Menlo does not host ISO forms because they are copyrighted by Insurance Services Office, Inc. You can read the real text through your own policy, which attaches every endorsement issued on it, or by asking your broker for the specimen your carrier files. Regulator-approved filings are also publicly viewable through SERFF Filing Access, the state filing system, though the forms there remain copyrighted and are for reading, not copying.
Frequently asked questions
Does CG 20 01 make someone an additional insured?
No. It only modifies the Other Insurance condition so coverage already granted to an additional insured applies on a primary and noncontributory basis. The additional insured status itself has to come from a separate endorsement such as CG 20 10 or CG 20 37.
Is certificate wording enough to make coverage primary and noncontributory?
No. A certificate of insurance is an information snapshot and changes no policy terms. The Other Insurance condition is modified only by an attached endorsement like CG 20 01 or equivalent carrier wording, so careful upstream parties request a copy of the endorsement along with the certificate.
What happens without CG 20 01 when two policies cover the same loss?
The CGL Other Insurance condition governs, and two primary policies share the loss by equal shares or pro rata by limits depending on what the other policy permits. That sharing is exactly what additional insureds want to avoid, which is why contracts demand the endorsement.
Does CG 20 01 apply without a written contract?
No. The endorsement operates only when a written contract or agreement requires your insurance to be primary and noncontributory. A verbal understanding or a contract signed after the loss does not trigger it.
This guide is for educational purposes and summarizes standard ISO policy language in Menlo's own words. Form numbers and titles are cited for identification only, and Menlo Insurance Services is not affiliated with Insurance Services Office, Inc. Your policy's specific terms, conditions, and endorsements control. Talk to a licensed broker about your actual exposures.