Aggregation under the SRA Minimum Terms explained
Reviewed by Matthew Bartlett, Director, Apex Insurance Brokers Limited · Last reviewed 2026-08-05
In short: Under the SRA Minimum Terms and Conditions (MTC), separate professional negligence claims against a solicitor can be treated as a single claim — aggregated — where they arise from one act or omission, or from related acts, matters or transactions. Aggregation changes how the limit of indemnity applies. Its precise meaning is shaped by case law, notably the Supreme Court in AIG Europe Ltd v Woodman (2017).
Aggregation is one of the most consequential ideas in solicitors' professional indemnity insurance, yet it rarely gets attention until something goes wrong. When several clients or several errors surface at once, whether they count as one claim or many can decide whether the firm's cover responds fully — or leaves a shortfall. This guide explains the concept behind aggregation in the SRA Minimum Terms and how the courts have interpreted it.
What the SRA Minimum Terms are
The Solicitors Regulation Authority (SRA) is the regulator for solicitors in England and Wales. It requires authorised firms to hold professional indemnity insurance that meets a baseline set of terms — the Minimum Terms and Conditions, usually shortened to the MTC. Insurers who cover the profession must offer cover that is at least as favourable as the MTC on the points the SRA prescribes.
The MTC set the floor, not the ceiling. They govern matters such as the minimum sum insured, who the cover must protect, and the limited circumstances in which an insurer can decline or reduce a claim. The minimum limit of indemnity is structured by firm type — a higher minimum applies to firms organised as bodies with limited liability than to other firms. Because these figures and rules can be revised, always check the SRA's current published MTC rather than relying on a remembered number.
What aggregation actually does
A professional indemnity policy carries a limit of indemnity — the maximum the insurer will pay. Aggregation is the mechanism that decides how many separate matters are gathered together and treated as one claim for the purpose of that limit.
The direction of travel matters enormously, and it cuts both ways:
- For the firm's own excess: aggregating several matters into one claim usually means paying a single self-insured excess rather than one per matter — helpful.
- For the limit of indemnity: aggregating many valuable claims into one can push the combined value against a single limit, risking a shortfall — potentially harmful. Kept separate, each claim would have its own limit to draw on.
So whether aggregation helps or hurts depends on the numbers, the excess, and how the limit is written. It is never simply "good" or "bad" — it is a rule about counting.
The structure of the MTC aggregation wording
The MTC set out the circumstances in which claims are to be regarded as a single claim. Conceptually, the wording groups claims together along a spectrum of connection. Without quoting clause numbers, the recognised limbs address claims arising from:
- one act or omission;
- one series of related acts or omissions;
- the same act or omission in a series of related matters or transactions; and
- similar acts or omissions in a series of related matters or transactions.
The first limbs are relatively intuitive: a single mistake, or a repeated mistake, that harms several clients. The final limb — similar acts or omissions across a series of related matters — is where most of the difficulty, and most of the litigation, has arisen. The key word is "related." Being merely similar is not enough; the matters or transactions themselves must be connected.
Unsure how your firm's limit and excess respond to a group of related claims? We arrange solicitors' PI cover and can walk you through it.
Get a PI quote →Why case law does the heavy lifting
The MTC state the aggregation test, but the words do not interpret themselves. What counts as a "series," and when matters are "related," has had to be settled by the courts. The leading authority is the UK Supreme Court's decision in AIG Europe Ltd v Woodman (2017), which examined the final limb of the aggregation wording.
In broad terms, the Supreme Court held that "a series of related matters or transactions" requires the transactions to be related to one another — not simply similar in character. The transactions have to be connected in some real way. The Court declined to confine that connection to a rigid formula such as the transactions being dependent on each other, treating relatedness as a question to be answered on the facts of each case.
The practical lesson is that aggregation is fact-sensitive. A group of conveyancing files handled the same way is not automatically one claim; nor is it automatically many. Whether the underlying matters are genuinely related to each other is what determines the outcome, and that assessment is made case by case.
Aggregated or not: how it plays out
| Scenario | Likely treatment | Effect on the limit |
|---|---|---|
| A single drafting error harming several clients in one transaction | One claim | All losses share one limit |
| Similar errors across separate, unconnected client matters | Likely separate claims | Each may have its own limit |
| Similar errors across matters that are genuinely related to each other | Potentially aggregated | Combined value tests one limit |
This table is illustrative only. The right answer in any real situation depends on the specific facts, the policy wording and, ultimately, the courts' interpretation of the MTC test.
What this means for your firm
Two points are worth carrying away. First, because aggregation can compress several claims against a single limit, firms with concentrated exposure — for example, similar work repeated across a related development, scheme or transaction — should think about whether their limit of indemnity is adequate, not just whether it meets the SRA minimum. The MTC minimum is a floor, and many firms sensibly buy well above it.
Second, aggregation is decided on facts you cannot always predict in advance. Good file management, clear engagement terms and prompt notification of circumstances all help, but they do not change the legal test. If you are weighing how much cover to carry, it is worth modelling the worst realistic aggregation scenario for your practice areas.
An experienced broker can help you pressure-test your limit against that scenario and place cover that reflects the true shape of your risk. Start a quote with Apex and we will talk it through.
Common questions
Does aggregation always reduce a firm's cover?
No. It can help by triggering only one excess across related matters, or hurt by forcing several valuable claims to share one limit. The effect depends on the amounts, the excess and how the claims relate.
Who decides whether claims aggregate?
Insurer and insured may agree, but where they disagree the aggregation wording is interpreted against the facts, applying principles set by the courts — most importantly the Supreme Court in AIG Europe Ltd v Woodman.
Is the aggregation wording the same for every solicitors' policy?
The core aggregation test comes from the SRA Minimum Terms, so it is common across the profession's compliant policies. Always read your own schedule and check the SRA's current published MTC for the exact terms and limits.
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.