What Is a Certificate of Insurance (COI) in Construction?

A certificate of insurance (COI) is a standardized summary document, usually ACORD 25, that lists a subcontractor's active liability policies, limits, and expiration dates. General contractors collect COIs to confirm coverage before mobilization; the COI is evidence at a point in time, not the insurance contract itself.

This guide is for general contractor compliance and operations leaders who manage subcontractor insurance across active job sites. You will learn what a COI proves, who issues and receives it, how it differs from policies and endorsements, what to verify on an ACORD 25, and when to request a new certificate.

Use the free subcontractor insurance requirements generator to publish limit floors and endorsement requirements brokers can resubmit against before your first COI review.

What is a certificate of insurance in construction?

Certificate of insurance (COI): A standardized summary document issued by a subcontractor's insurance broker or agent listing active liability policies, coverage limits, policy numbers, and expiration dates.

On construction projects, subcontractors carry general liability, workers compensation, and often automobile and umbrella policies. The GC does not hold those policies; the sub does. Instead, the GC collects a COI as proof that required coverage exists before crews mobilize.

COIs are the starting point for vendor compliance, not the finish line. A certificate tells you what policies are active on the date issued. It does not replace reading endorsements, confirming limits against your contract exhibit, or monitoring expiration dates through the project schedule.

Most GC programs require a COI at onboarding, before first mobilization, at policy renewal, and whenever entity structure or scope changes. Programs that treat "COI on file" as permanent clearance discover gaps when policies lapse mid-project or endorsements drop at renewal.

What does a COI prove, and what does it not prove?

Evidence of insurance: Documentation that a party carries active insurance coverage as of a stated date, used by GCs to make mobilization and clearance decisions before site access.

A COI proves that specific policies were in force when the certificate was issued. It shows named insured, carrier, policy numbers, limits, and effective dates. That is enough for an initial compliance review when paired with your contract requirements.

A COI does not prove:

• That coverage will remain in force through the full project schedule
• That endorsements required by your contract are attached to the policy
• That claim payment will occur if an incident happens
• That the named insured matches the entity actually performing work (without your verification)

GCs who rely on a COI alone, without checking endorsements or tracking expiration, often approve vendors who appear compliant on paper but lack required additional insured language or carry lapsed policies.

Who issues and who receives COIs on a construction project?

Certificate holder: The party named on the COI who receives notice if the underlying policy is cancelled or materially changed, often the general contractor and sometimes the project owner.

The subcontractor's insurance broker or agent issues the COI on behalf of the carrier. The sub requests it; the broker prepares the ACORD 25 and emails the PDF to the GC's compliance coordinator or project team.

The general contractor is typically listed as certificate holder and may also appear as an additional insured when contract requirements demand it. Owner requirements often flow down through the GC's subcontract: the GC's insurance exhibit becomes the sub's minimum standard.

A typical COI request flow:

1. GC sends insurance requirements (limits, endorsements, certificate holder language) to the sub at award or pre-mobilization.
2. Sub forwards requirements to their broker.
3. Broker issues ACORD 25 and any required endorsement copies.
4. GC compliance reviews the certificate against the contract exhibit before clearing the vendor.

Delays usually happen at step 3. Brokers need lead time, especially when additional insured endorsements require carrier approval. Publish your requirements early using a standardized checklist so subs and brokers know what to submit.

What should GCs look for on an ACORD 25?

ACORD 25: The industry-standard Certificate of Liability Insurance form that summarizes commercial general liability, automobile, umbrella/excess, and workers compensation policies on one page.

When reviewing a subcontractor COI, verify these fields line by line against your contract insurance exhibit:

1. Named insured matches the legal entity performing work (including DBA if applicable).
2. Policy effective and expiration dates cover the mobilization window, not only the contract award date.
3. General liability limits meet or exceed contract minimums (per occurrence and aggregate).
4. Workers compensation is listed with appropriate statutory limits or employer's liability if required.
5. Automobile liability appears when subs use vehicles on site or haul materials.
6. Additional insured checkboxes and description of operations reflect your program requirements.
7. Certificate holder lists the correct GC legal name and address.
8. Insurer A.M. Best rating or carrier identity meets any program floor your contract specifies.

Checkbox statements on ACORD 25 indicate that certain coverage types exist. They do not replace endorsement PDFs. When your contract requires additional insured status, waiver of subrogation, or primary/non-contributory language, request the underlying endorsement forms and review them against your approved list.

How is a COI different from a policy and an endorsement?

GC compliance programs involve three distinct document types. Confusing them is one of the most common sources of clearance errors.

Additional insured endorsement: An amendment to the subcontractor's liability policy that extends coverage to parties named in the endorsement (often the GC and owner) beyond what the base policy provides.

The COI is a pointer to coverage. The policy is the contract. The endorsement is the proof that specific parties or terms were added to that contract.

A sub can present a COI where the additional insured checkbox is marked, but the CG 20 10 / CG 20 37 endorsement (or state equivalent) is missing from the policy. GC reviewers who stop at the certificate approve vendors who lack the risk transfer their contract requires.

Read what is an additional insured endorsement before accepting COIs that claim additional insured status without the underlying form.

When do GCs need a new COI from a subcontractor?

COI collection is not a one-time onboarding task. Request and re-verify certificates at these points:

1. Onboarding and pre-award: Establish baseline coverage before contract execution or notice to proceed.
2. Pre-mobilization: Confirm policy dates still cover the mobilization window, especially when award and site start are months apart.
3. Policy renewal: Collect an updated certificate when general liability, workers comp, or auto policies renew. Renewals are a common point where endorsements disappear even when checkboxes still indicate coverage.
4. Entity or scope change: Reissue when the sub adds a DBA, merges operations, or changes legal structure. The named insured on file must match the entity performing work.
5. Mid-project expiration: When a policy term ends before project completion, block clearance until a valid renewal COI and endorsements are on file. See COI renewal monitoring for alert cadences.

Programs that collect COIs once and file them in a shared drive without expiration monitoring discover lapses at mobilization, owner audits, or incident reviews, when reconstruction is hardest.

Effective GC teams connect COI receipt to clearance status per vendor per project. Compliance owns the review standard; PMs and supers consume blocked, cleared, or pending status without searching email. For ongoing monitoring workflows, see COI tracking for general contractors.

A certificate of insurance is the document every GC compliance program revolves around, but it is only useful when reviewers understand what it proves, what it does not, and when to demand a fresh copy. Pair COI basics with a verification checklist and continuous expiration monitoring so field teams mobilize on current coverage, not stale files.

To see how centralized COI tracking connects clearance to mobilization gates, review the product overview. To discuss your program requirements, request a demo.