COI vs. W-9: What Documents to Collect From Vendors

The short version

A Certificate of Insurance (COI) proves a vendor carries insurance and protects you from liability if something goes wrong. A W-9 captures a vendor's tax identification information so you can report payments to the IRS. They solve completely different problems—and you generally need both from every paid vendor.

What a COI is for

The COI is a risk-management document. It summarizes a vendor's active insurance policies—general liability, workers' compensation, auto—along with coverage limits and expiration dates. Property managers use it to confirm a vendor can cover the cost of injury or damage they cause, and (via additional insured status) to extend that protection to the owner and management company.

• Collect it before the vendor performs any work.
• Verify coverage meets your requirement for that property.
• Confirm your entity is named as additional insured where required.
• Track the expiration date and re-collect on renewal.

What a W-9 is for

The W-9 is a tax-compliance document. It records the vendor's legal name, business structure, and Taxpayer Identification Number (TIN or EIN). You need it to issue a Form 1099 for reportable payments and to avoid IRS backup-withholding penalties. Unlike a COI, a W-9 does not expire—but it should be refreshed if the vendor's name, entity type, or TIN changes.

• Collect it during onboarding, before the first payment.
• Match the legal name and TIN to what the vendor invoices under.
• Re-collect if the business entity or ownership changes.

The complete vendor document set

COI and W-9 are the two everyone knows, but a complete onboarding packet usually includes more depending on the vendor type and property:

• Certificate of Insurance (general liability, and workers' comp / auto as applicable).
• W-9 for tax reporting.
• Trade or business licenses for licensed trades (electrical, plumbing, HVAC).
• Additional insured and waiver-of-subrogation endorsements where required.
• A signed service agreement defining scope and insurance obligations.

Collect and verify both in one flow

VendorSuite requests the full document set from each vendor through a single passwordless portal link, reads and structures every field automatically, and scores the vendor against your requirements—so the COI's coverage and the W-9's tax details are captured, verified, and monitored together instead of living in separate inboxes and folders.