Deloitte is a global professional services organisation and one of the “Big Four”, providing audit, tax and legal, consulting, financial advisory and risk advisory services through a network of independent member firms under the Deloitte brand.
At a glance
Founded: 1845 (London), by William Welch Deloitte
Global structure: Member firms of Deloitte Touche Tohmatsu Limited (DTTL), a UK private company limited by guarantee
Global revenue (FY2024): US$67.2bn
People: Around 460,000 globally
Presence: More than 150 countries and territories
Motto/purpose: “Making an impact that matters”
Overview
Deloitte operates a federated model: legally separate and independent member firms deliver services locally while drawing on DTTL’s global brand, methodologies and quality standards. This structure allows the organisation to combine local market knowledge with global scale, serving listed companies, privately held businesses, the public sector, and non-profits across industries.
History and evolution
The firm’s roots trace to 1845, when William Welch Deloitte opened his practice in London. Over the subsequent 19th and 20th centuries, the business expanded alongside the development of modern auditing and corporate reporting. Through mergers – most notably with Touche Ross in the late 20th century – and international expansion, Deloitte grew into a worldwide network with broad advisory capabilities while retaining independent local partnerships under a common global umbrella.
Services
Deloitte’s multidisciplinary model is organised around five broad areas, delivered with sector-specific expertise and shared technology assets:
Audit & assurance: External audit, reporting assurance, controls and sustainability assurance.
Tax & legal: Business and international tax, global employer services, indirect tax, transfer pricing, and legal services in permitted jurisdictions.
Consulting: Strategy, technology implementation, operations, cloud and enterprise applications, human capital, and customer transformation.
Financial advisory: M&A, valuations and modelling, infrastructure and real estate advisory, restructuring and turnaround.
Risk advisory: Enterprise, regulatory and forensic risk, cyber, data and digital trust.
Deloitte also operates alliance ecosystems with major technology vendors, and offers managed services that combine people, process and platforms to deliver outcomes over time.
Scale and market position
Deloitte is consistently the largest of the Big Four by global revenue and headcount. In the fiscal year ended 31 May 2024 it reported US$67.2bn in aggregate global revenues and a workforce of approximately 460,000 people worldwide. Its consulting business has ranked No. 1 by revenue in Gartner’s global market-share analysis in recent years, reflecting the breadth of its transformation and technology offerings.
How Deloitte is organised
“Deloitte” is a brand rather than a single international partnership. DTTL (incorporated in England and Wales as a company limited by guarantee) coordinates the network and sets global policies and standards, while each member firm is a separate legal entity subject to local laws and regulation. This model permits local ownership and regulation of audit practices, while enabling global methodologies, independence controls, technology platforms and learning to be shared across borders.
Clients and industries
Deloitte serves multinational groups, mid-market companies and fast-growth private businesses, as well as governments and public sector bodies. Sector coverage spans financial services; technology, media and telecoms; energy, resources and industrials; consumer; life sciences and health; and more. Services commonly combine audit quality, tax and legal structuring, digital transformation, data and AI, cyber resilience, sustainability reporting and transaction support.
Quality, regulation and independence
As an audit practice operating in many jurisdictions, Deloitte member firms are overseen by national audit regulators and subject to stringent independence and quality-management requirements. The network maintains global audit methodologies and systems of quality control, with regular internal and external inspections. In non-audit services, Deloitte emphasises risk management, data protection, and ethical conduct across its engagements.
People, culture and purpose
The organisation’s stated purpose—“making an impact that matters”—underpins programmes in learning and leadership development, diversity, equity and inclusion, and community impact. As a large employer of graduates and experienced professionals worldwide, it invests in technical upskilling (including data and AI), professional qualifications, and well-being initiatives, while offering global mobility opportunities across its member firms.
Notes for UK readers
In the UK, Deloitte LLP (the UK member firm) provides audit, tax, consulting, financial advisory and risk advisory services with national coverage and sector teams aligned to the UK market. The UK practice operates under the same global brand, independence rules and quality systems as the wider network, while complying with UK audit regulation and professional standards.
Last reviewed: August 2025
Latest coverage of Deloitte
