Primary and noncontributory
Wording that makes the contractor's policy pay first for the additional insured, without asking the additional insured's own policy to share the loss.
CG 20 01On the certificate
Usually a line in the description box. The ACORD 25 has no checkbox for it.
What to check
An endorsement such as CG 20 01 that applies when your written contract requires it, on the general liability policy and, if your requirements say so, the umbrella.
The common gap
The description box says "primary and noncontributory" and no endorsement backs it up, so your own policy ends up sharing the claim.
Go deeper on forsured.ai: What does primary and noncontributory mean on a COI?
Related: Additional insured · Waiver of subrogation · Try Spot the Gap
General information, not legal or insurance advice. Ask your broker what your policies actually carry.