CG 20 10 is the endorsement everyone knows to ask for. CG 20 37 is the one they forget, and it’s the one that protects you after the subcontractor leaves the site. If your contracts don’t require both, you carry real liability after closeout.
Here’s a scenario that happens to GCs more often than anyone publishes. A subcontractor finishes their scope on a commercial project. Their insurance looks compliant on the day of closeout, and everyone moves on. Eight months later a defect surfaces, maybe a waterproofing failure, a structural issue or an MEP problem, and a claim follows.
Your contract requires you to indemnify the owner, so you tender the claim to the sub’s insurer under their CG 20 10 endorsement. The carrier denies it. CG 20 10 only covers ongoing operations, and the sub’s work was finished months ago. You needed CG 20 37, and your contract never asked for it.
What Is CG 20 37?
CG 20 37 is an ISO endorsement officially titled “Additional Insured: Owners, Lessees or Contractors, Completed Operations.” Like CG 20 10, it attaches to a subcontractor’s Commercial General Liability policy and adds the GC, owner or developer as an additional insured. The difference is that it covers claims that arise after the sub’s work is complete.
The two endorsements are designed as a pair. CG 20 10 covers you while the work is happening. CG 20 37 covers you after it’s done. Together they give you continuous additional insured protection across the whole project.
ISO’s own structure confirms this: the standard ISO setup for construction additional insured status is CG 20 10 and CG 20 37, not one or the other. Requiring only CG 20 10 leaves a gap that opens the moment the sub walks off site.
CG 20 10 vs. CG 20 37: What Each Covers
| CG 20 10 | CG 20 37 | |
|---|---|---|
| Coverage period | During ongoing operations only | After operations are complete |
| Applies when | The sub is actively working on the project | The work is finished and the sub has left the site |
| Ends when | The sub’s work on that project is complete | The policy expires, or as stated in the endorsement |
| Main use | On-site incidents, bodily injury and property damage during construction | Defects found after completion, latent defects, warranty claims |
| Needed together? | Yes. CG 20 37 fills the gap after closeout. | Yes. CG 20 10 covers the build itself. |
| Covers the GC’s sole negligence? | No | No |
Why You Need Both, Not One or the Other
The gap between CG 20 10 and CG 20 37 is the gap between “while the crew is on site” and “for as long as your warranty runs.” On most commercial projects, that’s 5 to 10 years.
The most common mistake: contract language that says “provide additional insured status via CG 20 10” and never mentions CG 20 37. A sub can meet that requirement with a certificate that gives you no coverage after completion. They’ve met the letter of your contract, and you’re exposed for everything that happens after closeout.
What “completed operations” means in practice
A completed operations claim comes from the sub’s finished work, after they’ve left the site and been paid. Common examples:
- A waterproofing failure found in the first heavy rain after occupancy
- An electrical fault that causes a fire six months after completion
- Structural cracking traced to the concrete contractor two years later
- A plumbing leak from a bad install, found by the next trade during finishes
- An HVAC failure caused by an installation defect during commissioning
Every one of these falls under completed operations. Without CG 20 37, you hold that liability yourself.
Completed Operations and the Warranty Period
Most GC contracts carry warranty obligations that run 1 to 10 years after substantial completion, sometimes longer for specialty scopes. For that entire period, every sub’s completed operations coverage needs to stay active and compliant.
That creates a compliance problem most COI tracking platforms don’t address. Projects close out, vendor records go dormant, and nobody checks whether the subs’ policies, and their CG 20 37 coverage, are still in force for the full warranty window.
Billy’s warranty mode: Billy tracks post-project warranty compliance separately from construction-phase compliance. It keeps monitoring subcontractor COIs and endorsements for the full warranty period and sends renewal requests automatically. Most platforms stop at closeout, which leaves one of the biggest liability gaps in construction risk management unwatched.
How to Verify Your Subs Have CG 20 37
- Update your contract language. Require “additional insured status for both ongoing and completed operations via CG 20 10 and CG 20 37 or equivalent.” Don’t assume CG 20 10 implies CG 20 37.
- Request both endorsements at onboarding. Your prequalification form and COI request should name both endorsement forms.
- Read the endorsement, not just the COI. A COI that says “additional insured” doesn’t tell you which ISO forms are attached. Ask for the endorsement pages themselves.
- Check the completed operations policy period. Some subs carry completed operations on a “tail” policy with a limited term. Make sure the period covers your warranty obligations.
- Keep tracking it after closeout. Keep monitoring completed operations coverage for the full warranty period, not just until substantial completion. Most compliance tracking software for contractors stops at closeout, so check that yours keeps watching for the whole warranty window.
Verify CG 20 10 and CG 20 37 on every COI, automatically
Billy’s AI Review Assistant confirms both endorsements are present, checks edition dates, and flags whether you have ongoing and completed operations coverage on every document, in seconds.
See how it worksFrequently Asked Questions
Is CG 20 37 always separate from CG 20 10?
Yes. They’re separate ISO forms that cover separate time periods. Some carriers print them on one endorsement page and others issue them as separate documents. Either way, you need both for continuous additional insured coverage across the project.
How long should completed operations coverage run?
At least through your warranty period, which is typically 1 to 3 years on most commercial work. For projects with longer statutory or owner-required warranties, require completed operations coverage for the full term. Work with your broker to make sure your subcontract language matches each project’s warranty period.
What if a sub can’t get CG 20 37?
Some specialty or smaller subs have trouble getting CG 20 37 from their carrier. Flag it and resolve it before work starts, not after completion. If a sub truly can’t provide completed operations coverage, assess the risk carefully and document your decision.
