Following form

A following-form policy borrows its coverage terms from the policy underneath it. An excess liability policy written on a follow-form basis says, in effect, that it applies to the same losses, subject to the same conditions and exclusions, as the underlying policy, and then adds limit on top. If the primary general liability policy responds to a claim, the follow-form excess generally does too once the underlying limit is used up.

"Generally" carries weight. Most follow-form excess policies list exceptions: exclusions of their own for pollution, professional services or wage-and-hour claims, a different notice condition, or limits on defense. Where the excess policy is silent, the underlying wording controls; where it speaks, it wins. An umbrella, by contrast, often has its own insuring agreement that can be broader than the primary and may sit over a self-insured retention where the underlying has none.

In a tower of several layers, higher excess policies typically follow the first excess or umbrella layer, so a gap or exclusion there travels upward. Ask your broker for a form-by-form comparison, not just a limits schedule, and confirm the attachment point lines up with the underlying limit. The guide on umbrella vs excess liability explains the difference, and excess liability defines the coverage itself.