Additional insured (AI)
A person or company added to someone else's liability policy, usually the owner and the general contractor on a trade contractor's policy. Status comes from an endorsement, not from the certificate.
CG 20 10CG 20 37CG 20 38On the certificate
A "Y" in the ADDL INSD column and, often, a line in the description box. Neither one creates coverage by itself.
What to check
That the endorsement is attached and names, or automatically includes, the parties your contract requires. CG 20 10 covers ongoing operations, CG 20 37 covers completed operations, and CG 20 38 can extend status to other parties up the contract chain.
The common gap
The box is checked and no endorsement exists, or the endorsement covers ongoing work only and the project needs completed operations too.
Go deeper on forsured.ai: Does additional insured status cover you after the job is done?
Related: Completed operations · Primary and noncontributory · Try Spot the Gap
General information, not legal or insurance advice. Ask your broker what your policies actually carry.