Methodology and data
Where every number on auditor.ltd comes from: accounts filed at Companies House and Brønnøysundregistrene, how fees are read from them, how they are cleaned, and the floors below which nothing is published.
Sources
United Kingdom. Every company that files audited accounts with Companies House discloses the fee payable to its auditor in the notes. We hold 29,561 such fees after cleaning, with the auditor named on 2,236 distinct firms' behalf, and revenue for most of them. Fees are read from the filed accounts by a parser, and where the parser cannot resolve a figure, by a model reading the relevant page, with the page number and the sentence it came from kept as evidence.
Norway. Brønnøysundregistrene names the auditor and the accountant of every company and publishes revenue, assets and headcount for most. It does not publish the audit fee, so Norwegian pages compare appointments, places and client size, never fees. 144,578 auditor appointments across 412 firms.
Cleaning
Filed data is not clean data. Before anything is aggregated: a fee that is a year (the signature date read as a fee) is withdrawn and the filing re-read; a fee or revenue in £'000 is rescaled only when the result is plausible for the company's size, and only after a person has approved it; one firm's several spellings, and the signature blocks that get read as firm names, are folded onto one name; cities are spelled one way. Every cleaned value is kept beside the raw one, and every rule is versioned. A withdrawn value is absent from these pages, never replaced by a guess.
Floors
A firm is published with twenty or more mandates. A city with fifty or more fees. A sector with a hundred and fifty. A revenue band on a firm's or city's page with five or more fees. A firm's year-on-year change with twenty or more clients carrying two years. Below the floor there is no page and no figure. No page on this site describes one company, and the site's database role cannot read a company row.
Definitions
Median is the middle value; half of fees are above it and half below. Interquartile range is the middle half. Big 4 is Deloitte, EY, KPMG and PwC. Challenger firms are the forty or so national and regional networks; independent firms are everyone else. Fee as a share of revenue is the median of fee divided by revenue across companies with £1m or more of revenue. Year-on-year change is this year's fee against last year's on the same filing, median across a firm's clients.
Use
The aggregate tables are published as CSV under a Creative Commons Attribution licence on the open data page. Cite auditor.ltd and Benford. The underlying filings are public records; the cleaning and the aggregation are ours.
Last refreshed 10 September 2026. Data and analysis by Benford.