ICAEW PII aggregate limit: the 2.5× fee income formula in practice

~4 min read

Reviewed by Matthew Bartlett, Director · Last reviewed 2026-07-06

The signature feature of the ICAEW professional indemnity insurance regime for accountants is the 2.5× formula. Under the Professional Indemnity Insurance Regulations made under Bye-law 61, every firm in public practice must carry a limit of indemnity of at least the greater of £1.5 million or 2.5 times the firm's gross fee income for its last completed financial year, subject to a stated ceiling. That formula does two things. It sets a floor for the smallest practices, and it scales the compulsory minimum with turnover so that growing firms cannot outrun their compulsory cover. This entry works through the mechanics, the edge cases, and the practical points brokers and firms encounter at every renewal.

The formula step by step

The calculation runs in three steps. First, identify the firm's gross fee income for the last completed financial year — the year that has been closed off before the renewal date, not the current year in progress. Second, multiply by 2.5. Third, compare to the £1.5 million floor and take the higher figure. The result is the operative minimum sum insured under the ICAEW regulations for the coming policy year.

A firm with £300,000 of gross fees produces £750,000 under the formula, below the floor — so the operative minimum is £1.5 million. A firm with £800,000 of gross fees produces £2 million, above the floor. A firm with £2.4 million of gross fees produces £6 million. A firm with £10 million of gross fees produces £25 million, and at that point the regulations' stated ceiling may become material — the ceiling caps the compulsory minimum but does not cap the exposure the firm should actually insure against.

What counts as "gross fee income"

The regulations use the term "gross fee income" and the ICAEW guidance elaborates on what is and is not caught. Fees from all public practice work count — audit, assurance, tax, accountancy, insolvency, corporate finance advisory, tax investigation, valuation, expert witness, and any other engagement performed as an ICAEW member firm. Referral fees received from third parties for work introduced to another firm typically count. Disbursements passed through at cost do not count. VAT is stripped out. Where a firm is part of a network and issues one set of invoices centrally, only the fees attributable to the ICAEW-regulated entity are captured. Fees earned by a subsidiary or associate that is not itself in ICAEW public practice sit outside the calculation.

Care matters at the boundary. Fees on a matter that started in one financial year and continued into another are allocated by when they were earned or invoiced under the firm's revenue recognition policy — the regulations do not impose a bespoke revenue recognition regime. Firms that have restructured, taken on lateral partners, absorbed another practice, or shed a service line during the year need to recalculate carefully; the "last completed financial year" figure may not be representative of the current risk, and both the insurer and the ICAEW would expect a firm to insure above the strict formula in those circumstances.

Where the formula meets aggregation

The 2.5× figure is an each-and-every claim minimum. The regulations do not, in themselves, require the policy to be arranged on an "each and every claim" basis without aggregate — insurers may issue policies with an annual aggregate. Where they do, firms and brokers need to check that the aggregate limit is set at a level that survives the risk profile of the book. A £6 million each-and-every limit with a £6 million annual aggregate exposes the firm to a first-claim erosion of the whole layer.

Aggregation clauses interact with the formula in the other direction. Where multiple related claims arise from a single event, they may be treated as one claim under the aggregation wording. That helps if the aggregate limit is generous, and hurts if it is tight. Every accountants' PI wording deserves a specific aggregation review — the topic is discussed further in our entry on accountants PII aggregation.

Sizing above the compulsory minimum

The formula is a compliance floor, not a risk management answer. A tax practice with three FTSE-listed clients earning a total of £900,000 in fees carries a compulsory minimum of £2.25 million — but a single mis-advised group reorganisation on any one of those clients could generate a claim well into eight figures. A liquidator handling a £40 million estate has a compulsory minimum driven by fee income, but the claimant is the estate. A broker's job is to help the firm size the actual layer above the compulsory floor, and the sizing exercise is the same across professions: identify the largest single realistic loss, look at the last six years of notifications and reserves, and layer accordingly.

Worked example

Illustrative only. A four-partner ICAEW firm with £2.4m of fees renews on 1 June 2026. Compulsory minimum is £6m each and every claim (2.4 × 2.5). The firm carries a £6m primary layer under the ICAEW regulations. Its largest engagement is an ongoing pension scheme audit worth £180,000 a year, and its largest recent claim reserve (settled in 2023) was £420,000. On broker advice the firm places a £4m excess-of-£6m top-up layer with a second insurer, giving a £10m tower — significantly above the compulsory minimum but proportionate to the pension scheme audit exposure. Total premium sits within the firm's budgeted PI provision. This is illustrative — every firm should size to its own book.