Research
How our research works
One place for the data behind our research pages: where it comes from, what each term means, exactly how we count, what each figure is a share of, and what the data cannot show.
In short
Our list is companies on the Companies House register that chose an accountancy activity code (SIC 69201, 69202 or 69203): 63,661 companies, of which 54,295 are trading by our definition. Ownership comes from the people with significant control records, size from the staff number in filed accounts. Everything we count is a registered company, not a practice, and sole traders and partnerships are not included. Being on the list does not mean a company is a practising firm.
Data sources
| Source | What we take from it | Date of the file we used |
|---|---|---|
| Companies House bulk company file (Free Company Data Product)1 | Company name and number, status, incorporation date, registered office address, accounts type and activity (SIC) codes | 1 October 2026 |
| Companies House accounts data (Accounts Data Product)2 | The average number of employees in each company's latest accounts, and the date its accounting period ended | Accounts filed electronically from October 2025 to September 2026 |
| Companies House people with significant control snapshot3 | Who is listed as having significant control: individuals or companies, and the name of each company listed | 12 October 2026 |
Companies House describes the bulk company file as a snapshot of "basic company data of live companies on the register", and says only electronically filed accounts are in the accounts data.14 Companies House says it "imposes no rules or requirements on how the information on the public register is used".4 We have not yet found a Companies House page that names the licence for the bulk files themselves, so we do not state one here. We publish only Companies House facts and figures worked out from them. We never publish the names of individual owners.
Companies House publishes what companies file. Since March 2024 it can query and remove information it believes is wrong, but a record on the register is not a guarantee it is accurate.5
Definitions
- Company: one record on the Companies House register.
- Practice: the accountancy business itself, which may run several companies. We have not yet matched companies into practices, so none of our figures count practices.
- Firm: the word we use for a practice in plain copy. Our page titles use "firms" as the everyday word; the figures on them are companies.
- Trading: status "Active" on Companies House, leaving out companies whose accounts are recorded as dormant. 54,295 companies. This is our label for the status shown; it does not prove a company is doing accountancy work.
- Dormant: Companies House records the company's accounts as dormant accounts, whatever its status. 6,261 companies.
- Not active: not dormant, and any status other than "Active", such as being struck off, in liquidation or in administration. 3,105 companies.
How we classify firms explains why we chose our size bands and ownership types, and what each cannot tell you.
Counting rules
Who is on the list
A company is on our list if any of the activity codes it gives Companies House is 69201 (accounting and auditing), 69202 (bookkeeping) or 69203 (tax consultancy). Each company is counted once, by its company number.
Ownership
- Only individuals listed as owners: every current person with significant control on the register is an individual.
- Owned through a holding company: at least one company is listed as a person with significant control, and the first company listed controls fewer than 3 companies on our list.
- Part of a group: the first company listed as a person with significant control controls 3 or more companies on our list, whatever their status.
- No ownership record: the snapshot holds no person with significant control for the company.
We use only the first company listed. 241 trading companies list more than one company as a controller. We do not trace owners above the company listed, so groups are undercounted. These are working categories, not a full ownership analysis. On this rule, 776 trading companies are part of a group, and the first company listed for them is one of 193 different companies.
Size
Size comes from the average number of employees in the company's latest accounts in the accounts data. Our bands are Micro (1 to 2), Small (3 to 20), Medium (21 to 100) and Large (over 100). They are our bands, not the legal size categories in company law. A company whose accounts show 0 employees gets no band and is counted separately: 8,180 trading companies. 13,344 trading companies have no staff number in the accounts data for that period and also have no band.
Age
Company age is the time from the incorporation date on Companies House to the date the figures were built. We group it as under 2 years, 2 to 4, 5 to 9, 10 to 19, and 20 years or more. It is company age, not practice age.
Shared addresses
A shared address is a registered office postcode where 20 or more trading companies on our list are registered. Addresses like these can be company formation agents or virtual offices. We have not checked each one, so some real firms are left out with them. We leave shared addresses out of area figures, but not out of the UK figures.
London and other areas
Each company's registered office postcode is matched to its local authority using postcodes.io, a free service that says it is updated with data from Ordnance Survey and the Office for National Statistics. London means Greater London (the 32 London boroughs and the City of London): 11,981 trading companies after leaving out shared addresses, with 4,009 more at shared addresses. Each area page states exactly which council areas it covers. Until 13 October 2026 London used only the inner postcode areas E, EC, N, NW, SE, SW, W and WC.6
What each figure is a share of
Every percentage on our research pages is shown with its count. This table sets out the total each kind of figure is a share of, in the current release.
| Figure | Share of | Companies |
|---|---|---|
| Ownership shares (UK) | All trading companies | 54,295 |
| Company age shares (UK) | All trading companies | 54,295 |
| Size band shares (UK) | Trading companies whose latest accounts show 1 or more staff | 32,771 |
| Companies by year of incorporation | All companies on our list, whatever their status | 63,661 |
| London ownership and age shares | Trading companies in the London subset | 11,981 |
| London size band shares | Trading companies in the London subset with 1 or more staff | 7,091 |
What the data cannot show
- Sole traders and partnerships: they are not on the company register, so they are not on our list.
- Companies with other activity codes: an accountancy business that chose a different code is missed.
- Practices with several companies: one practice can run several companies, so counts of companies are not counts of practices, and a practice's staff can sit on a company we do not see.
- Indirect ownership: we see only who is listed directly. Owners above that company, and every shareholder, are not shown.
- Paper accounts: the accounts data covers only electronically filed accounts, so some companies have no staff number.
- Quality: nothing here says how good a firm is, or which firm suits your business.
How often figures are refreshed
Companies House says it updates the bulk company file within 5 working days of the end of each month.1 How often we rebuild our figures will be stated with each release. Each research page shows the dates of the files it was built from. We keep a copy of the files each release is built from, so its figures can be rechecked.
How to cite our research
Please name the page, The Right Accountant and the date of the data, for example: The Right Accountant, "Who owns UK accountancy firms", data from Companies House 12 October 2026. Our research pages each show a citation line.
How to report an error
If a figure or a company record looks wrong, see Corrections. Facts that come from Companies House have to be corrected at Companies House. Our editorial policy sets out how we check facts.
Our research pages
- Who owns UK accountancy firms: Ownership types, from the people with significant control records.
- How big UK accountancy firms are: Staff numbers from filed accounts, in our size bands.
- How old UK accountancy firms are: Company age, which is not the same as practice age.
- Accountancy firms in London: A defined subset: central and inner London postcode areas, shared addresses left out.
- Online fixed-fee accountants compared: Prices as published on each firm's own website, with the date we read them. Not built from Companies House data.
Sources
- Companies House, Free Company Data Product (bulk company file dated 1 October 2026). download.companieshouse.gov.uk/en_output.html. Checked 13 October 2026.
- Companies House, Accounts Data Product (electronically filed accounts only). download.companieshouse.gov.uk/en_monthlyaccountsdata.html.
- Companies House, People with significant control snapshot (downloaded 12 October 2026). download.companieshouse.gov.uk/en_pscdata.html.
- GOV.UK (Companies House), "Companies House data products". gov.uk/guidance/companies-house-data-products. Checked 13 October 2026.
- GOV.UK (Companies House), "Companies House begins phased roll-out of new powers to tackle fraud", 4 March 2024. gov.uk/government/news/companies-house-begins-phased-roll-out-of-new-powers-to-tackle-fraud. Checked 13 October 2026.
- postcodes.io. postcodes.io. Checked 13 October 2026.