How we work and match
How we classify firms
We describe each accountancy company on our list by size, ownership and age. This page sets out the exact rule for each one, why we chose it, and what it cannot tell you.
The short answer
Size comes from the staff number in a company's latest filed accounts, in four bands we chose ourselves: Micro (1 to 2), Small (3 to 20), Medium (21 to 100) and Large (over 100). These are not the legal size categories. Ownership comes from the people with significant control on Companies House. Age is the time since the company was incorporated, which is not the same as how long the practice has been running.
Companies, not practices
Every rule on this page applies to a company: one record on the Companies House register. A practice, the accountancy business itself, may run several companies, and a group may own many practices. Until we match companies into practices, everything we classify is a company. Sole traders and partnerships are not on the company register, so they are not on our list.
Our list is companies on the Companies House register that chose an accountancy activity code (SIC 69201, 69202 or 69203).4 Being on it does not mean a company is a practising firm. Companies House publishes what companies file. Since March 2024 it can query and remove information it believes is wrong, but a record being on the register does not guarantee it is accurate.
Size bands
We use the staff number in the company's latest filed accounts: the average number of employees the accounts show. We take it from accounts filed electronically between October 2025 and September 2026, using Companies House accounts data.1
| Band | Staff number | In plain terms | Trading companies |
|---|---|---|---|
| Micro | 1 to 2 | One or two people. | 21,960 (67%) |
| Small | 3 to 20 | A small team. | 10,234 (31.2%) |
| Medium | 21 to 100 | A larger team. | 540 (1.6%) |
| Large | Over 100 | More than 100 staff on this one company. | 37 (0.1%) |
Shares are of the 32,771 trading companies with a staff number. 13,344 of the 54,295 trading companies have no staff number in that period and have no size band.
Why these bands
These bands are our choice. We picked them because they match questions a business owner may have when choosing a firm:
- 1 to 2: you may deal with the same one or two people for everything, and there may be no one else to cover when they are away.
- 3 to 20: there is a team, so work can be shared, but it is still a small business.
- 21 to 100 and over 100: the firm is big enough to have separate teams, and possibly specialists, but you may deal with more than one person.
None of these is better than another. The right size depends on what your business needs.
How they differ from the legal size categories
Company law has its own size categories, used for what accounts a company files. GOV.UK says a company is a micro-entity if it has any 2 of: a turnover of £1 million or less, £500,000 or less on its balance sheet, and 10 employees or less. It is small if it has any 2 of: a turnover of £15 million or less, £7.5 million or less on its balance sheet, and 50 employees or less.2
We do not use those categories for two reasons. First, we only have the staff number, not turnover or balance sheet figures, so we cannot apply the legal tests. Second, the legal tests would put a one-person company and a ten-person firm in the same category, and that difference matters when you choose an accountant. When we say "Micro" or "Small", we mean our bands, not the legal categories.
What size cannot tell you
- The staff number belongs to one company. A practice that employs its people through another company can show few or no staff on this one.
- It is an average for the accounting period, and accounts periods end on different dates. It can be out of date.
- It does not say how many qualified accountants work there, or how good the work is.
Ownership types
We use the people with significant control (PSC) records on Companies House, from the snapshot dated 12 October 2026.3 Each trading company gets one of four labels:
| Label | Rule | Trading companies |
|---|---|---|
| Only individuals listed as owners | Every current person with significant control on the register is an individual. No company is listed. | 50,178 (92.4%) |
| Owned through a holding company | At least one company is listed as a person with significant control, and the first one listed controls fewer than 3 companies on our list. | 2,805 (5.2%) |
| Part of a group | The first company listed as a person with significant control also controls 3 or more companies on our list. | 776 (1.4%) |
| No ownership record | Companies House holds no current person with significant control for the company. | 536 (1%) |
Shares are of all 54,295 trading companies.
What ownership cannot tell you
- These are working categories based on the first company listed as a controller. 241 trading companies list more than one company; we use only the first.
- We do not trace the owner above the company listed. A group that holds firms through middle companies will look smaller than it is, or look like several owners, so groups are undercounted.
- The record may not show indirect ownership or every shareholder. A holding company may be the owners' own company; the record does not prove it either way.
Company age
Company age is the time from the incorporation date on Companies House to 12 October 2026, the date we built these figures. We group it into five bands: under 2 years, 2 to 4 years, 5 to 9 years, 10 to 19 years, and 20 years or more.
What company age cannot tell you
Company age is not practice age. A practice that traded as a sole trader or partnership for years may have formed its company recently. A practice may also set up a new company when it restructures or is bought, so a long-running firm can sit behind a young company. Where a page shows "company formed", it means the date of that company, not when the practice started.
Trading, dormant and not active
- Trading: status "Active" on Companies House, leaving out companies that file dormant accounts. 54,295 companies.
- Dormant: Companies House records the company's accounts as dormant accounts, whatever its status. 6,261 companies.
- Not active: not dormant, with any status other than "Active", such as being struck off, in liquidation or in administration. 3,105 companies.
"Trading" is our label for the status shown. It does not prove the company is doing accountancy work.
Sources
- Companies House, Accounts Data Product (electronically filed accounts only). download.companieshouse.gov.uk/en_monthlyaccountsdata.html. Checked 12 October 2026.
- GOV.UK, "Annual accounts: micro-entities, small and dormant companies". gov.uk/annual-accounts/microentities-small-and-dormant-companies. Checked 12 October 2026.
- Companies House, People with significant control snapshot (downloaded 12 October 2026). download.companieshouse.gov.uk/en_pscdata.html.
- Companies House, Free Company Data Product (bulk company file dated 1 October 2026). download.companieshouse.gov.uk/en_output.html. Checked 12 October 2026.