COI and W-9: The Difference and What to Collect From Vendors

Last updated July 2026.

A COI and a W-9 are not the same thing and they do not protect you from the same problem. A certificate of insurance is evidence that a vendor carries insurance, and it protects you from liability. A W-9 is an IRS form that gives you a vendor's taxpayer identification number, and it protects you from a tax reporting penalty. Most businesses need both from most vendors, and they expire on completely different schedules.

They get confused because they arrive in the same email, during the same onboarding step, from the same person in accounts payable. Then a year later somebody realizes the certificate lapsed in March and nobody noticed, because the W-9 in the same folder never expires and the folder looked complete.

Is a COI and a W-9 the same thing?

No. A W-9 is a one page IRS form the vendor fills out itself, giving you its legal name, tax classification and taxpayer identification number so you can issue a 1099 at year end. A certificate of insurance is issued by the vendor's insurance agent and shows what coverage the vendor carries, with what limits, through what dates. Different issuer, different purpose, different expiration.

What is the difference between a COI and a W-9?

The cleanest way to see it is side by side.

Note the row that causes the most damage: the COI expires and the W-9 does not. A vendor file that was complete on day one is quietly incomplete twelve months later, and only one of the two documents is responsible.

What does COI mean?

COI stands for certificate of insurance. It is a one page summary, almost always on the ACORD 25 form, issued by a vendor's insurance agent to show that policies exist. It lists the carriers, policy numbers, coverage types, limits, and effective and expiration dates, and it names the certificate holder.

What matters most is what a certificate is not. It is not an insurance policy and it does not grant anyone coverage. It is evidence, and it comes with disclaimer language on its face saying exactly that. If your contract requires you to be an additional insured, the document that actually makes you one is the endorsement, not the certificate. That distinction is covered in additional insured vs certificate holder, and it is the difference between thinking you are covered and being covered.

What is a W-9 form used for?

Form W-9, Request for Taxpayer Identification Number and Certification, collects the information you need to report what you paid a vendor to the IRS. The vendor supplies its legal name, any business name, its federal tax classification, its address, and its taxpayer identification number, which is either a Social Security number or an employer identification number. Then it signs.

You do not send the W-9 anywhere. You keep it, and you use it at year end to issue Form 1099-NEC for nonemployee compensation. The W-9 is the input; the 1099 is the output.

Has the 1099 threshold changed?

Yes, and this is the detail most vendor onboarding guides still have wrong. The federal reporting threshold for Form 1099-NEC and Form 1099-MISC rose from 600 dollars to 2,000 dollars for payments made on or after January 1, 2026, under the One Big Beautiful Bill Act. Starting in 2027 that figure is adjusted annually for inflation and rounded to the nearest 100 dollars.

This does not mean you can stop collecting W-9s from small vendors. You almost never know in January what a vendor will be paid by December, and chasing a W-9 from a contractor who has already been paid and has stopped answering the phone is a genuinely miserable task. Collect it before the first payment goes out, every time, whatever the expected amount.

Do you need both a COI and a W-9 from every vendor?

Nearly always, but for different reasons, and the exceptions do not overlap. Collect a W-9 from any vendor you pay. Collect a certificate of insurance from any vendor whose work can create liability for you, which means anyone who comes on site, touches your property, handles your customers or your data, or does work you could be sued over.

A software company you pay by credit card needs a W-9 and probably not a COI. A landscaping crew with a ride on mower needs both, urgently. A consultant who never visits needs a W-9, and a COI if the contract says so.

Which vendors need to give you a W-9?

Request one from every vendor before the first payment. Some payees are exempt from 1099 reporting, most notably corporations, but the exemptions have holes worth knowing: payments to attorneys for legal services and payments for medical and health care services are reportable even when the payee is a corporation. Since the exemption analysis depends on information that is on the W-9 itself, the only workable rule is to collect the form first and apply the rules afterwards.

Which vendors need to give you a certificate of insurance?

Anyone whose work could produce a claim against you. In practice that means contractors and subcontractors, anyone performing services on your premises, delivery and logistics providers, staffing agencies whose workers you direct, professional service firms carrying errors and omissions exposure, and any tenant or facility user whose activities your own policy would otherwise absorb.

The requirement should come from your contract, not from a habit. Set minimum limits and required coverages by vendor type, put them in writing, and then check every arriving certificate against them. The full checklist is in vendor insurance requirements.

What happens if you pay a vendor without a W-9?

If a vendor will not provide a taxpayer identification number, you are required to begin backup withholding at 24 percent of reportable payments and remit that money to the IRS. You also expose yourself to penalties for filing an information return with a missing or incorrect TIN. Neither outcome is catastrophic on one invoice, and both are entirely avoidable by collecting the form before the first payment rather than the last.

What happens if you pay a vendor without a valid COI?

Nothing, until something happens. Then the vendor's uninsured claim looks for the nearest solvent party, which is you, and your own carrier pays a loss it never priced for. In a workers compensation audit, an uninsured subcontractor's payroll can be reclassified as yours, which produces a premium bill that arrives long after the job is finished. The mechanics are in what happens when a vendor's insurance expires.

This is the asymmetry worth internalizing. A missing W-9 costs you a predictable, bounded penalty. A missing COI costs you whatever the claim happens to be.

What other documents belong in vendor onboarding?

Beyond the certificate and the W-9, most programs collect a signed contract or master services agreement, business and professional licenses where the work is regulated, and the additional insured endorsement when the contract requires it. Regulated industries add more: background checks, HIPAA training and immunization records for hospital vendors, safety qualification for construction subcontractors.

At year end, the pieces come back together. You reconcile what you actually paid each vendor against the 1099s you are about to issue, which usually means pulling twelve months of payment history out of the bank and into the books. If that reconciliation lives in QuickBooks, the statements behind it can be converted straight into a QuickBooks ready file instead of being keyed in line by line.

The one that needs a system

Here is the practical difference between the two documents. A W-9 is a one time collection problem. Once you have it, you have it, and the folder stays complete.

A certificate of insurance is a recurring collection problem forever. It expires every year, sometimes mid term when a policy is cancelled, and the vendor has no incentive to tell you. Every certificate you have ever collected is decaying toward useless on a schedule you did not choose. That is why W-9 collection is a checklist item and COI tracking is a system: reminders before expiry, rules that check limits and coverages against your requirements, and a record you can produce years later when a claim surfaces.

If you are running that on a spreadsheet today, vendor insurance compliance software automates the reading, the checking and the chasing, and manual COI tracking vs software covers the point where the spreadsheet stops working.