Deloitte vs EY
Side-by-side comparison of AI visibility scores, market position, and capabilities
London global professional services (largest Big 4) at $70.5B FY2025 revenue (+4.8%); Anthropic strategic alliance with Scout AI tool and 460,000 employees serving 90% Fortune 500 competing with PwC and Accenture for consulting and audit mandates.
About
Deloitte Touche Tohmatsu Limited (DTTL) is a London, England-headquartered global professional services network — operating as the world's largest professional services firm by revenue, reporting $70.5 billion in aggregate global revenue for fiscal year 2025 (ended May 31, 2025, +4.8% in local currency) with approximately 460,000 employees across 150+ countries — providing audit and assurance, consulting, tax and legal, risk advisory, and financial advisory services to nearly 90% of the Fortune 500 and 8,500+ US private companies. Consulting represents 40%+ of total revenue as Deloitte's largest service line. Global CEO Joseph Ucuzoglu has led the firm since January 2023. Key AI initiatives include the strategic alliance with Anthropic (using Claude for client engagements and internal operations), the Scout AI research tool for client strategy engagements, and $2+ billion in AI capability investment. Founded with roots to 1845 when William Welch Deloitte opened his London accounting office; modern Deloitte formed through the 1989 merger of Deloitte Haskins & Sells with Touche Ross.
Big Four professional services partnership at $51.2B FY2024 revenue (+3.9%); CEO Janet Truncale launched EY.ai Agentic Platform with NVIDIA (150 agents, 80K professionals) competing with Deloitte and PwC for global audit and consulting.
About
EY (Ernst & Young) is a London-based global professional services partnership — one of the Big Four accounting and consulting firms — generating $51.2 billion in record annual revenue in fiscal year 2024 (+3.9%), with approximately 393,000 professionals operating across more than 700 offices in over 150 countries and territories. EY's roots trace to 1903 when Alwin C. Ernst and Theodore Ernst founded Ernst & Ernst in Cleveland, Ohio; the modern EY emerged from the historic 1989 merger of Ernst & Whinney and Arthur Young & Co. EY's integrated service model spans assurance (the highest-revenue segment among Big Four peers), consulting, strategy and transactions through EY-Parthenon (created via the 2014 acquisition of The Parthenon Group), and tax services. In July 2024, Janet Truncale became EY's Global Chair and CEO, the first woman to lead the firm. In 2025, EY launched the EY.ai Agentic Platform in partnership with NVIDIA, deploying 150 AI agents supporting 80,000 EY professionals across tax, risk, and finance domains to surpass 3 million tax compliance outcomes annually.
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