Top-Up (Excess Layer) PI Cover Explained
Reviewed by Matthew Bartlett, Director, Apex Insurance Brokers Limited · Last reviewed 2026-08-05
Many firms buy a single professional indemnity (PI) policy and assume that limit is fixed. It is not. When your work exposes you to claims larger than your current limit — a big contract, a demanding client, or a regulator's minimum — you can add a top-up layer rather than replacing your whole programme. This page explains how excess layer PI cover works, how the layers respond to a claim, and when a top-up makes sense.
What "excess layer" actually means
Your primary layer is your first PI policy — say £2m. A top-up (also called an excess layer or excess of loss policy) sits directly on top of it. If your primary is £2m and you buy a £3m top-up, your total limit becomes £5m.
The key rule is order of response. The excess layer does not pay from pound one. It is only triggered once the layer beneath it — the primary — has been used up by paid claims. Insurers call this the attachment point: the excess layer "attaches" at £2m and covers the band from £2m to £5m.
How a claim moves through the layers
Imagine a firm with a £2m primary policy and a £3m top-up, facing a settled claim of £3.5m:
- The primary insurer pays the first £2m (less any policy excess you owe).
- The excess layer insurer pays the remaining £1.5m, because the loss has passed the £2m attachment point.
- Both layers are within limit, so the firm is fully protected.
If the claim had been £6m, the two layers would pay £5m combined and the firm would carry the final £1m itself — a reminder that even a top-up has a ceiling.
"Follow form" and why wording matters
Most excess PI policies are written on a follow form basis. This means the excess layer follows the terms, conditions and exclusions of the primary policy beneath it, so the two respond consistently to the same claim. A genuine follow-form policy avoids the trap where a loss is covered by the primary but excluded higher up.
Where the top-up is placed with a different insurer, watch for gaps. Some excess wordings add their own conditions or exclusions, and a mismatch — a "difference in conditions" — can leave a slice of a claim uninsured. Aligning the aggregate limits, the retroactive date and the definition of "claim" across both layers is exactly the sort of detail a broker checks before you bind.
Not sure whether one large limit or a primary plus top-up is better value for your firm? We compare both.
Get a PI quote →Primary plus top-up vs. one large policy
You can reach £5m of cover two ways: a single £5m primary policy, or a £2m primary with a £3m top-up. Neither is automatically better — it depends on price, appetite and how insurers view your risk.
| Single large primary | Primary + top-up | |
|---|---|---|
| Cost per £ of limit | Higher at the top end | Excess layers often cheaper |
| Insurer appetite | One insurer must take the whole risk | Spreads risk across insurers |
| Administration | One policy, one renewal | Two policies to keep aligned |
| Flexibility | Fixed limit | Add or drop a layer as needs change |
When a top-up makes sense
- A contract demands more limit. A client or public-sector framework may require, say, £5m of PI while your standard cover is £2m. A top-up meets the requirement without over-insuring the rest of your work.
- A single large project. Consultants and construction professionals often need extra limit for one high-value job — sometimes on a project-specific basis.
- Regulatory minimums. Some regulated professions set minimum limits. Solicitors' firms, for example, must hold cover on the Solicitors Regulation Authority (SRA) Minimum Terms and Conditions, and many buy top-up cover above that compulsory layer. RICS-regulated surveyors face minimum PI requirements too.
- Your primary insurer won't go higher. If your existing insurer caps its appetite, an excess layer with another insurer bridges the gap.
Aggregate limits and "erosion"
Most PI policies — primary and excess — are written in the aggregate, meaning the limit is the most the insurer pays across all claims in the policy year, not per claim. Several claims in one year can erode your primary limit, at which point the excess layer starts to respond to later losses even if no single claim exceeds £2m. This is why the total programme limit, not just the primary, matters when you assess exposure.
PI is also almost always written on a claims-made basis, so the policy that responds is the one in force when the claim is made, not when the work was done. Keeping the retroactive date consistent across your primary and top-up protects cover for past work.
If you are weighing whether to add an excess layer, start a quote and tell us your required limit — we will structure the layers so they respond as one.
Common questions
Does a top-up policy pay before my primary?
No. An excess layer only responds once the primary limit beneath it is exhausted by paid claims. Until the attachment point is reached, the primary insurer handles the claim.
Can my top-up be with a different insurer from my primary?
Yes, and it often is. The important thing is that the excess wording follows the primary form, and that limits, retroactive dates and key definitions line up so there is no gap between the two layers.
Is buying a top-up cheaper than increasing my primary limit?
Frequently, yes. Because excess layers are less likely to be called upon, they can cost less per pound of limit than the equivalent extra primary cover — but this varies by profession and risk, so both routes are worth comparing.
Apex Insurance Brokers Limited is authorised and regulated by the Financial Conduct Authority (FRN 724952). This guide is general information, not advice on a specific policy or a substitute for your policy wording.