What are defence costs in professional indemnity insurance?

Reviewed by Matthew Bartlett, Director, Apex Insurance Brokers Limited · Last reviewed 2026-08-05

What "defence costs" actually covers

Professional indemnity (PI) insurance responds when a client, or a third party, alleges that your professional advice, design or service caused them a financial loss. Two very different things can then happen. The claim might be valid, in which case the insurer may pay damages or a settlement. Or the claim might be weak, exaggerated or simply wrong — but you still have to answer it. That answering is where defence costs come in.

Defence costs are the reasonable expenses of investigating, defending or settling a claim against you. In practice that typically includes:

• Solicitors' fees for advising you and handling correspondence with the claimant.
• Barristers (counsel) instructed to advise or represent you at a hearing or trial.
• Expert witnesses — for example another surveyor, engineer or accountant giving an opinion on whether you fell below the expected standard.
• Court fees and, where a defence fails, an order to pay the other side's legal costs.
• Investigation and evidence-gathering to work out what actually happened.

Crucially, cover is usually triggered by a valid notification of a claim or of circumstances that might give rise to one — not by a court finding you liable. That is the whole point. Defending yourself is expensive whether or not you did anything wrong, and the policy exists to fund that defence.

Why you're covered even if the claim fails

A common misconception is that PI only pays out "if you're found negligent". The opposite is closer to the truth: the greatest practical value of PI is often in claims where you did nothing wrong. An aggrieved client can allege a loss, instruct solicitors and force you into a defence regardless of the merits. Someone has to pay the lawyers to demonstrate that the allegation doesn't stand up.

Under most UK PI wordings, once a claim is properly notified the insurer takes on — or funds — the defence, including where the allegation is ultimately shown to be baseless, is withdrawn before trial, or is settled without any admission of liability. You should always check your own policy, because the trigger and the insurer's rights are defined by the wording, but the principle is standard: a spurious claim can still be a very costly one, and the policy is designed to meet that cost.

If you're weighing up how much cover you actually need, it can help to talk it through and get a PI quote from Apex rather than guess from a comparison page.

Why defence costs can exceed the damages

It surprises people that the legal bill for defending a claim can be larger than the sum the claimant was ever chasing. There are structural reasons for this:

• Professional negligence is technical. Establishing whether you met the standard of a reasonably competent professional usually needs expert evidence on both sides — and experts are expensive.
• Litigation is slow. A dispute can run for months or years through correspondence, disclosure of documents, witness statements and, occasionally, trial. Costs accrue at every stage.
• Winning still costs money. Even a successful defence rarely recovers every penny of your own legal spend from the other side, and getting to "we won" still meant paying counsel and experts along the way.
• Multiple parties. Where several professionals are blamed for the same loss, the arguments — and the costs — multiply.

The upshot: a claim seeking, say, £40,000 in damages can generate a defence bill running well into six figures if it is fought hard. That is precisely why the way defence costs interact with your policy limit is not a technicality — it can decide whether your cover is enough.

Costs-in-addition vs costs-inclusive: the difference that matters

UK PI policies handle defence costs in one of two ways, and it materially changes how much protection you have. The distinction is sometimes labelled "costs in addition" versus "costs inclusive" (or "costs within the limit").

Costs in addition (defence costs paid on top of the limit). Here your limit of indemnity is preserved for damages and settlements, and reasonable defence costs are paid separately, in addition. If you hold a £1m limit and a claim settles for £1m, your defence costs don't eat into that £1m — they are met over and above it. This is the more protective structure for the policyholder, because a heavy defence bill can't erode the money available to actually settle the claim.

Costs inclusive (defence costs paid within the limit). Here defence costs and damages share the same limit. If your limit is £1m and defending the claim consumes £300,000 in legal and expert fees, only £700,000 remains to meet a settlement or award. A hard-fought claim can therefore leave you exposed even though the headline limit looked adequate on day one.

Neither approach is "wrong" — but you need to know which one you have, because it changes the real-world value of the number on your schedule. Some sectors and some regulators effectively push towards costs-in-addition arrangements or set minimum terms; solicitors' PI in England and Wales, for example, is governed by the SRA's Minimum Terms and Conditions, which shape how cover including defence costs must operate. Always read the wording, or ask your broker to confirm it in plain English.

The excess, and who controls the defence

Two related points often come up alongside defence costs.

How the excess applies. Your policy excess (the amount you pay before the insurer contributes) may apply to damages only, or to defence costs as well — wordings vary. Where the excess bites on costs too, you carry the first slice of the legal spend. This is worth checking, because it affects your out-of-pocket exposure on even a modest claim.

Who runs the defence. On most PI policies the insurer has the right to take over and conduct the defence, appointing solicitors from its panel. That generally works in your favour — specialist defence lawyers, paid for by the insurer — but it also means you should notify early and cooperate. Trying to handle a claim yourself, or admitting liability, before telling your insurer can prejudice cover.

Notification: why timing protects your defence costs

PI is almost always written on a "claims made" basis, meaning it responds to claims first made against you (and notified) during the policy period, regardless of when the work was done. That makes prompt notification essential. If you become aware of a circumstance that could turn into a claim — an unhappy client, a hint of a mistake, a threatening letter — telling your insurer promptly can bring the future claim within the current policy, and with it the funding for your defence. Delay can hand the insurer grounds to decline. The Insurance Act 2015 sets the framework for a policyholder's duty to make a fair presentation of the risk and governs the remedies available for breach, which is another reason to be candid and timely with your broker and insurer.

Larger or more complex risk? Speak directly to a director — call 0117 325 0027 or email info@apexinsurancebrokers.co.uk.

Common questions

Are defence costs paid even if the claim against me is withdrawn?
Yes, in most cases. Once a claim or circumstance is validly notified, the reasonable costs of defending it are generally covered even where the claimant withdraws, drops the matter, or the allegation is shown to be unfounded. Cover turns on a valid notification, not on you being found liable — but the exact trigger is set by your wording, so check it.

How do I know whether my defence costs are "in addition" or "inclusive"?
Look at your policy schedule and wording, or ask your broker. A costs-in-addition policy pays defence costs on top of your limit, preserving it for settlement. A costs-inclusive policy pays them from within the limit, reducing what's left for damages. If it isn't obvious, treat that as a question to resolve before renewal.

Does my excess apply to defence costs?
Sometimes. On some policies the excess applies only to damages or settlements; on others it also applies to defence costs, so you carry the first part of the legal spend. It depends on the wording, and it's a sensible thing to confirm so you know your true exposure on a small claim.

Defence costs are one of the least understood but most valuable parts of PI cover. The number on your schedule tells you the limit; the wording tells you whether that limit is really yours to spend on a settlement, or whether your own lawyers get there first. If you're not sure which you have, ask Apex to check it for you.

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 reading your policy wording.