Top 10 Accounting Firms in the UK: What Makes Each Firm Different?
From the Big Four to fast growing mid tier firms, see how the UK's largest accounting firms compare and which suits your business.
The UK's largest accounting firms fall into two clear groups, the Big Four, who dominate audit and large corporate work and a tier of mid-sized firms who compete on sector specialism, regional presence and service for owner managed businesses. Together these 10 firms make up most of what people mean when they search for the best accounting firms UK wide, though which one is actually right for you depends far more on your own situation than on where a firm sits in a revenue table.
This guide breaks down who these firms are, what genuinely separates them beyond size and why a top 10 firm isn't automatically the right choice for every business. If you're specifically looking at options closer to home, our comparison of top accountancy firms in Bristol covers a more regional set of choices.
In This Article
Quick Comparison
| Firm | Tier | UK Revenue (Latest Filed) | Known For |
|---|---|---|---|
| PwC | Big Four | £6.35bn | Largest UK firm by revenue, global reach |
| Deloitte | Big Four | £5.68bn | Largest accounting network globally |
| EY | Big Four | £3.78bn | Financial services, energy, technology |
| KPMG | Big Four | £2.99bn UK standalone, £3.6bn combined with Switzerland since 2024 | Risk management, technology partnerships |
| BDO | Mid tier | £1.0bn | SME and enterprise tax and advisory |
| Evelyn Partners | Mid tier | £656.6m | Accountancy combined with wealth management |
| Grant Thornton | Mid tier | £654.0m | Mid market audit and advisory |
| RSM | Mid tier | £522.0m | Wide UK office network, cross border support |
| Azets | Mid tier | £405.0m | Widest UK geographic spread, SME focus |
| Forvis Mazars | Mid tier | £362.4m | Public interest entity audit specialism |
Figures reflect each firm's most recently published financial results as reported directly by the firm, using the reporting period ending in 2025 in each case. Reporting periods vary slightly between firms, so figures aren't perfectly like for like.
The Big Four: Who They Are and Why They Dominate
The Big Four dominate the UK accounting market largely because of their reach into large corporate audit work. Between them, PwC, Deloitte, EY and KPMG handle the vast majority of FTSE 350 audit fees, a scale no mid tier or specialist firm can realistically compete with.
PwC
PwC is currently the UK's largest accounting firm by revenue, having reported £6.35 billion for the year ended 30 June 2025. It was formed in 1998 through the merger of Price Waterhouse and Coopers and Lybrand, though both firms trace their roots back to the mid 1800s.
- UK Consolidated Group revenue of £6.35 billion for the year ended 30 June 2025, up slightly on the previous year
- Operates in more than 150 countries as part of the wider global PwC network
- Known as one of the most prestigious employers in UK accounting and finance
Deloitte
Deloitte sits close behind PwC and remains the largest accounting network globally by revenue, though its UK business had a notably tougher year recently.
- UK revenue of £5.68 billion for the year ended 31 May 2025, a 1 percent decline, the firm's first UK revenue drop in 15 years
- Heavy investment in digital transformation, cybersecurity and sustainability advisory
- Client base spans the FTSE 100, public sector bodies and fast growing private companies
EY
EY is particularly known for its work in financial services, energy, technology and consumer products, and reported UK growth in a year several competitors found difficult.
- UK fee income of £3.78 billion for the year ending 27 June 2025, up 2 percent
- Strategy and Transactions grew 10 percent, while Consulting revenue fell 6 percent, reflecting a mixed year across service lines
- Strong focus on ESG advisory, helping clients build sustainability into their operations
KPMG
KPMG rounds out the Big Four, though its UK reporting changed significantly after merging with KPMG Switzerland in October 2024.
- Reported £2.99 billion in its final year as a standalone UK entity, for the year ended 30 September 2024
- Following the merger, the combined KPMG UK and Switzerland Group reported £3.6 billion for the year ended 30 September 2025, so this figure includes Switzerland and isn't directly comparable to a UK only number
- Uses Microsoft, Oracle, SAP, Salesforce and IBM platforms to support audit and compliance services
The Mid-Tier Firms Closing the Gap
Below the Big Four sits a group of firms that, while smaller in revenue, often provide more accessible and specialised service for mid sized and owner managed businesses. Several of these firms have posted stronger year on year growth than the Big Four recently, closing the gap in certain sectors even if not in overall scale.
BDO
BDO, established in 1903, is the largest firm in this tier by some distance.
- UK revenue of £1.005 billion for the year ending 4 July 2025, broadly stable on the previous year
- Recently announced plans to merge with BDO Ireland, with the combined entity expected to reach around £1.1 billion in revenue
- Services include corporate tax, VAT, payroll, financial reporting advisory and HMRC compliance, using platforms including Xero and QuickBooks
Grant Thornton
Grant Thornton focuses heavily on mid market audit and advisory work and recently took on private equity investment of its own to fund growth.
- UK fee income of £654.0 million, up 7.2 percent year on year
- Positioned as an alternative to the Big Four for larger mid market businesses
- Around 5,500 staff across the UK
Evelyn Partners
Evelyn Partners stands out for combining traditional accountancy with wealth management services under one roof, and now edges narrowly ahead of Grant Thornton in this tier.
- UK fee income of £656.6 million, up 9.3 percent year on year
- Backed by private equity investors Permira and Warburg Pincus
- Useful for clients who want tax and accountancy advice alongside investment and financial planning
RSM
RSM has one of the widest UK footprints of any firm in this tier.
- UK fee income of £522.0 million
- Around 5,420 staff across roughly 30 UK locations
- Part of a global network spanning more than 120 countries, particularly suited to businesses with cross border operations
Azets
Azets has the broadest geographic spread of any firm on this list and grew rapidly from a standing start.
- UK fee income of £405.0 million
- Launched in 2017 with private equity backing and grown through the acquisition of close to 100 accountancy firms
- Serves a large base of SME and owner managed business clients across the widest UK office network of any firm here, the kind of business that often also needs a straightforward way to work out annual salary figures for staff or director pay
Forvis Mazars
Forvis Mazars, formerly known simply as Mazars, is recognised as a leading auditor for public interest entities in the UK following its recent merger with Forvis.
- UK fee income of £362.4 million
- Offers a balanced range of audit, accounting, tax, financial advisory and consulting services
- Strong presence in statutory audit work for larger regulated organisations
What Actually Separates These Firms Beyond Revenue
Revenue tells you about scale, but it doesn't tell you much about fit. When comparing any list of accountancy firms UK wide, a few other factors matter more for most businesses.
Sector Specialism
Some firms lean heavily into financial services or large corporate audit, while others focus on SMEs, owner managed businesses or specific industries, including practical needs like calculating monthly salary correctly for payroll.
Geographic Spread
A firm with dozens of regional offices, like Azets or RSM, may offer easier in person access than one concentrated in major cities.
Growth Rate and Investment
Faster growing mid tier firms are often investing heavily in technology and expanding their advisory services beyond basic compliance.
Ownership and Structure
Some of these firms are structured as single consolidated entities, while others operate as networks of independent regional practices, which can affect consistency of service across locations.
Why Revenue Rankings Don't Tell You Which Firm is Right for You
A firm's position in a UK top accountancy firm's ranking reflects its overall size and client base, not how well it will serve your specific situation. A billion pound firm built around FTSE 350 audit work has very different priorities, pricing and client attention than a business needs from an accountant handling routine compliance and practical tax advice.
Larger firms generally suit large corporations, businesses needing statutory audit or companies with genuinely international operations. Smaller and mid sized businesses often find they get more attention, faster response times and more tailored advice from a firm sized appropriately to their needs, rather than a large practice where they represent a small fraction of the client base, particularly for situations like IR35 status that a generalist firm may not prioritise in the same depth.
Does Your Business Actually Need a Top 10 Firm?
For most sole traders, contractors and small business owners, the honest answer is no. A Big Four or mid tier firm is built to serve large, complex organisations and a small business often ends up as a minor client within a much bigger practice, without the specialist attention a dedicated smaller firm can offer.
This is exactly the gap a specialist practice fills. Henleaze Tax Consultancy, based in Bristol, works specifically with contractors, sole traders, landlords and small limited companies, offering fixed fee pricing and direct access to advice tailored to how these businesses actually operate, including IR35 status and salary and dividend planning that a larger generalist firm may not prioritise.
Looking for Dedicated, Fixed-Fee Accounting Support?
Get in touch with our specialist Bristol team for straightforward tax advice, transparent monthly pricing, and tailored accounting support.
Frequently Asked Questions
Figures in this guide are based on publicly available information at the time of writing and may vary slightly depending on the reporting period used by each firm. For advice specific to your own business, particularly as a contractor or small limited company, speak with a qualified accountant directly.