A Certificate of Insurance (COI) is a one-page summary document — usually the ACORD 25 form — that shows a contractor's active insurance policies, coverage limits, and expiration dates at the time the certificate was issued.
For general contractors, it is the first document you request from every subcontractor. It is also the document most teams mishandle: filed once, never re-checked, and mistaken for actual coverage.
How does a COI work?
A subcontractor asks their insurance agent to issue a certificate to the GC. The agent fills out the ACORD 25 using the sub's current policy information, lists the GC as certificate holder, and sends the PDF as evidence of insurance.
The GC then reviews the certificate against the contract requirements:
- Does the named insured match the subcontractor?
- Are the required coverage types listed?
- Do limits meet the contract?
- Are the policies active for the work period?
- Are required endorsements attached or confirmed?
That review is where compliance happens. A COI certificate is the starting evidence, not the approval by itself.
What a COI actually proves
A COI confirms that insurance existed on the date the certificate was created. It lists:
- Named insured (legal business name)
- Insurance carrier and policy numbers
- Coverage types (general liability, workers' comp, auto, umbrella)
- Per-occurrence and aggregate limits
- Effective and expiration dates
- Certificate holder (who received the proof)
What it does not do:
- Amend or extend the underlying policy
- Guarantee coverage will exist when a claim happens
- Make the certificate holder an additional insured (unless backed by an endorsement)
- Replace W-9s, licenses, or signed subcontracts
For subcontractor-specific workflows, see what GCs need to collect on a subcontractor certificate of insurance.
State insurance regulators treat COIs as informational documents only. The policy language — and endorsements attached to it — controls what is actually covered.
Why remodeling GCs need COIs on every sub
On a typical kitchen remodel or whole-home renovation, you might have 8–15 subcontractors across trades: demo, framing, electrical, plumbing, HVAC, drywall, tile, paint, and specialty vendors.
If an uninsured sub injures someone on your jobsite, damages the client's property, or has an employee injury, the claim often flows upstream. Your GL policy, your client relationship, and your contract indemnity clauses all get tested at once.
Collecting a COI before mobilization is how you document that the sub carried required coverage during the work period. Without it, you have no evidence — and auditors, owners, and carriers will notice.
COI vs policy vs endorsement
| Document | What it is |
|---|---|
| COI (ACORD 25) | Snapshot proof of coverage |
| Insurance policy | The actual contract with the carrier |
| Endorsement | A modification to the policy (additional insured, waiver of subrogation, etc.) |
Many compliance failures happen because a COI mentions additional insured status in the description box, but the endorsement was never issued. The certificate note does not create coverage.
Read more: COI vs endorsement — why the certificate isn't enough.
What to collect besides the COI
Before a sub starts work, most GC compliance packets include:
- Current COI matching contract limits
- W-9 for 1099 reporting (W-9 and COI guide)
- Additional insured endorsements when required (CG 20 10 and CG 20 37)
- Signed subcontract with insurance requirements
- License (where applicable for the trade and state)
How often to refresh COIs
Policies renew annually — often mid-project. A COI valid on day one can be expired by month six.
Best practice:
- Log every policy expiration date at onboarding
- Request updated certificates 30 days before expiration
- Suspend site access if coverage lapses without a replacement COI
Manual spreadsheets rarely sustain this. That is why GCs adopt COI tracking tools with automated renewal reminders.
Bottom line
A COI is necessary, but it is only the starting point. Verify limits, endorsements, named insured accuracy, and expiration dates — then keep monitoring through project completion.
FAQ
What is a COI certificate?
A COI certificate is another way people refer to a certificate of insurance. In construction, it usually means an ACORD 25 showing a contractor's active liability policies.
What does COI mean in construction?
COI means certificate of insurance. GCs use it to confirm subcontractors carry required insurance before they start work.
Does a COI make the GC an additional insured?
No. The COI may reference additional insured status, but the endorsement on the policy is what grants it.
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