The W-9 and the COI are the two documents every general contractor should collect from subcontractors before the first dollar is paid or the first truck hits the driveway.
They solve different problems — tax reporting vs insurance compliance — but they must align. When the W-9 legal name does not match the COI named insured, you have a problem that shows up in January (1099 penalties) or in litigation (coverage disputes).
What each document does
W-9 (Request for Taxpayer Identification)
- Establishes legal name and federal tax ID (EIN or SSN)
- Documents entity type (LLC, S-Corp, sole prop, etc.)
- Required for 1099-NEC reporting when you pay a sub $600+ in a calendar year
- Should be collected before first payment, not in December
COI (Certificate of Insurance)
- Proves active insurance on the date issued
- Lists GL, WC, auto, umbrella limits and expiration dates
- Names certificate holder and may reference additional insured endorsements
- Must be verified, not just filed — see verification guide
Why collect them together
| Risk if W-9 missing | Risk if COI missing / expired |
|---|---|
| IRS penalties for incorrect 1099s ($310+ per form) | Uninsured claim exposure on your jobsite |
| Backup withholding obligations | Owner / lender compliance failure |
| Payment delays at year-end | Indemnity disputes with upstream parties |
IRS construction-sector enforcement on 1099 reporting remains aggressive. On the insurance side, industry analyses consistently find a significant share of COI submissions contain at least one coverage gap — wrong limits, missing endorsements, or expired dates.
Unified onboarding catches both.
Name matching rules
The legal name on the W-9 must match:
- Subcontract agreement signatory entity
- COI named insured field
- Checks / ACH payee name
Variations that cause rejections:
- "John Smith" on W-9 vs "Smith Plumbing LLC" on COI
- Missing "LLC" or "Inc."
- DBA used on COI but not on W-9
Fix at onboarding — not when the auditor or adjuster asks.
7-step collection process
- Send onboarding packet with W-9 template + insurance requirements schedule
- Collect W-9 before scheduling mobilization
- Collect COI meeting your limits and endorsement requirements
- Cross-check names across W-9, COI, and contract
- Verify COI (limits, AI endorsements, dates) — not just receive
- Log expiration dates for every policy line on the COI
- Set renewal triggers for W-9 updates (entity changes) and COI renewals (annual)
Renewal and refresh cadence
- W-9: Refresh annually in Q4 before 1099 season; immediately on entity changes
- COI: Refresh at every policy renewal; monitor expirations continuously during long projects
- Mid-year changes: New coverage types, carrier switches, or limit changes require updated certificates immediately
W-9 + COI in one upload flow
Subs forget attachments. GCs chase in email. Project managers start work without both docs because the schedule is hot.
Better flow:
- Single magic link with checklist: "Upload COI" + "Upload W-9" + "I don't have this yet" with reason
- GC reviews documents in one place with requirements visible
- System blocks "approved" status until required items are complete
CoiLoop supports this checklist model for remodeling GCs who manage 15–50 subs across active projects.
FAQ
Can I pay a sub without a W-9?
You should not. Without a valid TIN, you may need to begin backup withholding and still face penalties if 1099s are wrong.
Is a COI enough if the sub says they're insured?
No. Verbal assurance is not evidence. You need a current COI matching contract requirements, with endorsements confirmed when required.
Related: Subcontractor compliance checklist · What is a COI?