A subcontractor certificate of insurance is the proof document a general contractor requests before a sub starts work. In construction, that usually means an ACORD 25 certificate showing the subcontractor's general liability, workers' comp, auto, and umbrella coverage.
The COI is necessary, but it is not the whole compliance file. A certificate tells you coverage existed when the agent issued it. It does not make you an additional insured, change the policy, or guarantee the sub will stay insured through the project.
What a contractor COI should show
Most contractor COIs include:
| COI field | What the GC should verify |
|---|---|
| Named insured | Matches the subcontract, W-9, and legal business name |
| Coverage types | GL, workers' comp, auto, and umbrella when required |
| Limits | Meet or exceed the insurance exhibit in the contract |
| Policy dates | Active before mobilization and not expiring mid-project |
| Certificate holder | Your correct legal entity and mailing address |
| Description of operations | Project, additional insured wording, waiver, and PNC notes |
If any of those items are missing or inconsistent, the certificate should go back to the sub or their agent with specific correction notes.
Why GCs collect COIs from subcontractors
General contractors collect subcontractor COIs to prove that risk is not quietly moving upstream. If a sub damages property, injures someone, or brings uninsured employees onto the jobsite, your own policy and contract obligations can be pulled into the claim.
A clean COI workflow helps you:
- Document that insurance was active before work began
- Confirm the sub meets minimum limits in the contract
- Catch expired policies before a crew arrives
- Store certificates and endorsements for owner or carrier audits
- Re-request renewals before coverage lapses
For a deeper definition of the document itself, start with what a certificate of insurance is.
The certificate is not enough by itself
The biggest mistake is approving a subcontractor because the COI says "additional insured" in the description box.
That box is informational. The actual coverage change comes from the endorsement attached to the policy. For construction, the common additional insured forms are CG 20 10 and CG 20 37.
At minimum, collect or confirm:
- COI on the current policy term
- Additional insured endorsement when required
- Primary and noncontributory endorsement when required
- Waiver of subrogation endorsement when required
- W-9 with a legal name that matches the insured
This is why certificate holder and additional insured are not interchangeable. Certificate holder means you received the proof. Additional insured requires policy language.
Construction COI checklist before work starts
Use this quick review before any subcontractor gets site access:
- Is the sub's legal name consistent across the subcontract, W-9, and COI?
- Is general liability active with the required occurrence and aggregate limits?
- Is workers' comp present, or is a valid exemption certificate on file?
- Is commercial auto required for this scope, and is it listed?
- Is umbrella or excess liability required by the owner contract?
- Are all policy expiration dates after the expected work window?
- Does the certificate holder box list the right GC entity?
- Are additional insured, waiver, and PNC endorsements attached or confirmed?
If the job will run past any expiration date, set a renewal reminder before approving the file. A COI that is valid on day one can become a gap halfway through the project.
Common subcontractor COI rejection reasons
GCs commonly reject contractor COIs when:
- The insured name is a DBA, but the subcontract is signed by a different legal entity
- General liability limits are below the contract minimum
- Workers' comp is missing for a sub with employees
- The certificate holder is the owner, lender, or old GC instead of your company
- Additional insured is mentioned on the COI, but no endorsement is attached
- The policy expires before the sub's scope is complete
- Umbrella coverage is required but not listed
Specific rejection notes get fixed faster than "please send an updated COI." Tell the sub exactly which field failed and whether the agent needs to reissue the certificate.
How to request a subcontractor certificate of insurance
Send requirements before the sub is scheduled. Include:
- Your legal certificate holder name and address
- Minimum limits by coverage type
- Required endorsements and form numbers
- Project name and location to show in the description box
- Upload link or email destination
- Deadline before mobilization
If you need a template, use the workflow in how to request COIs from subcontractors.
How CoiLoop helps
CoiLoop gives each sub a no-login upload link, stores the COI and W-9 together, reads key certificate fields, and lets the GC approve or reject against a checklist. It also tracks expiration dates so renewals do not disappear in email.
That keeps subcontractor insurance compliance tied to the work you are actually awarding, not a spreadsheet someone has to remember to update.
FAQ
What is a subcontractor certificate of insurance?
It is a COI issued by the subcontractor's insurance agent showing active policies, limits, dates, and certificate holder information. GCs use it as proof that the sub carries required coverage.
Is a contractor COI the same as an insurance policy?
No. The COI summarizes coverage. The policy and endorsements control the actual insurance rights.
Can a subcontractor start work before sending a COI?
They should not. Letting a sub start before proof of insurance shifts risk back to the GC and can breach owner or lender requirements.
How often should subcontractor COIs be updated?
At every policy renewal and whenever contract requirements change. Many GCs request updated certificates 30 days before expiration.
Related guides: Subcontractor COI compliance checklist · How to verify a subcontractor COI · Track subcontractor insurance expirations