Attachment point

~3 min read

Category: Liability programme structure · Reviewed by the Apex broking team · Last reviewed 2026-08-20

In short: The attachment point is the level of loss at which an excess layer begins to pay — normally the top of the underlying limit beneath it. Whether and when a layer attaches depends on how the underlying limit is eroded: by claims alone or by defence costs as well, by single losses or by an aggregate of several, and on what the excess wording accepts as proper exhaustion of the layer below.

Category: Liability programme structure Also known as: attachment, layer attachment, excess point Related concepts: follow form excess, excess liability insurance

Definition

In a layered insurance programme, each excess layer sits above a stated amount of underlying cover. That stated amount is the layer’s attachment point: the layer responds to the part of a loss that exceeds it, up to the layer’s own limit. A layer written as “£5m excess of £5m” attaches at £5m and provides the next £5m of cover.

Erosion of the underlying limit

The practical questions all concern how the underlying limit is used up:

Costs in addition or costs inclusive. Where defence costs are payable in addition to the primary limit, the limit erodes only by damages; where costs are inclusive, legal spend eats the limit and the excess layer is reached sooner. The excess layer’s own basis should match, or the tower’s arithmetic goes wrong in the middle of a claim.
Any-one-claim or aggregate. Under an any-one-claim primary, each claim has the full limit and the layer attaches only if a single claim (as aggregated by the wording) exceeds it. Under an aggregate primary, a run of smaller claims can erode the limit so that the excess layer drops down to respond to later claims — if its wording provides for drop-down.
Exhaustion provisions. Some excess wordings attach only when the underlying insurer has actually paid its full limit. Settlements below the primary limit, an insolvent primary insurer, or a coverage dispute below can then leave a loss stranded between layers.

How it works in practice

Attachment points are chosen when a programme is structured: the primary insurer’s appetite sets the first limit, and excess layers are stacked above at attachment points that follow each layer’s top. The buyer’s interest is that the points line up exactly — no gap between the top of one layer and the attachment of the next — and that each layer’s erosion and exhaustion language is consistent with the layer below. This is close kin to the follow form question: a layer that attaches at the right number but on different terms may still fail to pay.

Aggregation matters too. Whether several related claims count as one claim determines whether they pierce an any-one-claim attachment point. The same facts can attach a layer under one aggregation wording and not under another.

Why it matters

An excess layer is bought for the bad day when losses climb past the primary. The attachment point, and the rules for reaching it, decide whether that layer is genuinely continuous cover or a number on a schedule. Reviewing erosion, drop-down and exhaustion language across the tower is a wording exercise a broker should complete before the layers are bound, not after a claim tests them.

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Apex Insurance Brokers serves UK professional services firms and commercial businesses. Call 0117 325 0027, email info@apexinsurancebrokers.co.uk, or request a quotation.

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