CG 20 10 vs CG 20 37: the additional-insured endorsement difference that quietly costs GCs

If you hire subcontractors, you've seen "CG 20 10" and "CG 20 37" on a certificate of insurance — or you've required them in a contract without being 100% sure what each one does. The distinction is small on paper and expensive in practice. Here's the plain-English version.

The one-sentence difference

• CG 20 10 adds you as an additional insured for liability arising out of the subcontractor's ongoing operations — while the work is being performed.
• CG 20 37 adds you as an additional insured for completed operations — claims that arise after the job is finished.

Why "after the job is done" is the dangerous part

In construction, the most expensive claims often surface after completion: a roof leaks the next winter, a deck fails, a weld cracks, water damage shows up months later. These are completed-operations claims. If your subcontractor's policy names you as additional insured only via CG 20 10 (ongoing ops), their carrier can decline to defend you on that later claim — and it rolls back onto your own policy and your loss history.

That's why most well-drafted construction contracts require both CG 20 10 and CG 20 37. Requiring only one is among the most common — and most quietly costly — gaps in subcontractor insurance compliance.

The trap: the certificate is not the proof

Here's what burns even careful GCs. On the ACORD 25 certificate, an agent can check the "ADDL INSD" box or type additional-insured language into the "Description of Operations." That box and that text are claims, not proof. The coverage only actually exists if the endorsement form itself (CG 20 10 and/or CG 20 37) is attached to the policy.

So a certificate can show "additional insured – yes," while the actual endorsement is missing, the wrong edition, or ongoing-operations only. To truly verify, you have to request and read the endorsement forms — not just trust the checkbox.

The endorsements that usually travel together

Contracts that require additional-insured status almost always require two companions, and you should verify them the same way:

• Primary & non-contributory — the subcontractor's policy pays first, before yours.
• Waiver of subrogation — the subcontractor's insurer agrees not to come after you to recover what it paid.

Additional insured (CG 20 10 + CG 20 37), primary & non-contributory, and waiver of subrogation are the "big four" you're really checking on a subcontractor's general liability.

A quick verification routine

1. Confirm the GL limits meet your contract (commonly $1M each occurrence / $2M aggregate; $2M+ for higher-risk trades).
2. Confirm the policy is active through your project's end date — not expiring mid-job.
3. For additional insured, don't accept the checkbox: request the actual CG 20 10 and CG 20 37 endorsement forms and confirm the edition and that your entity is named (or that it's a blanket form triggered by written contract).
4. Confirm primary & non-contributory and waiver of subrogation the same way.
5. Re-check at every renewal.

We put the full version of this into a free, no-signup Subcontractor COI Verification Checklist — print it and run it against your next certificate.

This article is general information, not insurance or legal advice. Endorsement requirements vary by contract and jurisdiction; confirm specifics with your broker or counsel.