The practical answer
Being an 'additional insured' on a vendor's general liability policy means their insurance defends and covers you for liability arising from their work. It's the single most demanded protection in commercial contracts — and the most commonly faked-by-checkbox on certificates.
Two ISO endorsement forms do most of the work, and the difference between them decides whether you're covered after the job is done.
CG 20 10 — ongoing operations
The CG 20 10 ('Additional Insured — Owners, Lessees or Contractors — Scheduled Person or Organization') covers you for liability arising from the vendor's ONGOING operations — while the work is happening. The moment the work is completed, CG 20 10 coverage generally stops. Editions matter: the 1985 edition was broader; post-2004 editions narrow coverage to liability caused at least in part by the insured's acts.
CG 20 37 — completed operations
Most construction defect and injury claims surface AFTER completion — the deck fails a year later, the wiring shorts after handover. That's completed operations liability, and it needs the CG 20 37 ('Additional Insured — Completed Operations'). Construction contracts typically require both forms: 20 10 for the build, 20 37 for the years after.
Verifying additional insured status properly
The verification checklist:
- The endorsement forms (or carrier equivalents) are physically attached behind the certificate — the ADDL INSD checkbox proves nothing.
- Scheduled endorsements name your exact legal entity; blanket endorsements require a written contract in place — make sure yours qualifies.
- Both ongoing (CG 20 10) and completed operations (CG 20 37) forms are present when your contract requires completed-ops coverage.
- Form editions and policy numbers match the certificate face.
Keep coverage decisions human and evidence explicit
CoverWarden records submitted evidence, requirements, findings, and authorized decisions. It does not issue coverage, guarantee claim outcomes, or replace your broker, attorney, or risk professional.
What teams usually ask
What is a blanket additional insured endorsement?
An endorsement that grants AI status automatically to any party the named insured agreed in a written contract to add — no schedule needed. It's convenient, but your protection then depends on having a signed contract with AI language before the loss.
Does additional insured status cover my own negligence?
Generally no under modern forms — post-2004 ISO editions limit coverage to liability caused in whole or part by the named insured's work. Your own sole negligence stays on your own policy.