Grant Thornton has agreed to acquire New York-listed management consulting firm CBIZ in a proposed $5 billion all-cash transaction, marking one of the largest deals of its kind in the accountancy sector and creating the fifth-largest professional services firm in the United States.

CBIZ, the only audit firm currently traded on the US stock market, will be acquired by backers of Grant Thornton Advisors — specifically, private equity firm New Mountain Capital. The deal follows a year in which CBIZ's share price has fallen nearly 40 percent, reaching a low of $24.29 in April.

Under the terms of the transaction, CBIZ shareholders will receive $55 per share, representing a 54 percent premium over the company's 30-day average share price. The deal is expected to close in the fourth quarter of 2026, after which CBIZ will cease to be publicly traded and will operate as a private company.

The combined entity will operate across more than 20 countries and generate nearly $7.5 billion in revenue, propelling Grant Thornton past its mid-market competitors to become the fifth-largest professional services, tax, and advisory provider in the US. That ranking places it directly behind the Big Four — Deloitte, PwC, EY, and KPMG — which have long dominated the top tier of the professional services market. Mid-tier firms have faced growing pressure to scale up as they compete with the Big Four for talent, technology investment, and large enterprise clients.

Jim Peko, chief executive of Grant Thornton Advisors, said: "By combining our multinational platform with CBIZ's strong market presence, we're broadening our ability to support businesses through every stage of growth — from early development to global scale."

Jerry Grisko, president and chief executive officer of CBIZ, added: "Joining Grant Thornton Advisors accelerates the realisation of that vision, creating a stronger firm with new and exciting opportunities for our team members and enhanced service offerings for clients, while delivering significant value to CBIZ shareholders."

As part of the agreement, CBIZ's Benefits and Insurance Services segment will be spun off into a new, standalone entity, which New Mountain Capital will also back.

Private Equity's Growing Role in the Industry

The transaction follows a broader wave of private equity investment sweeping the accountancy sector. Grant Thornton's UK arm recently became the largest UK professional services business to accept external equity investment after agreeing to be acquired by private equity firm Cinven. On Tuesday, it was reported that Grant Thornton's UK equity partners received a £35.2 million payout tied to the large external stake.

Private equity investment in the accountancy sector has surged in recent years, drawn by the industry's predictable, recurring revenue streams and a fragmented market that offers consolidation opportunities. London-based Blick Rothenberg is widely recognised as the first major UK accountancy firm to receive private equity backing, following HgCapital's investment in July 2016. Chief executive Nimesh Shah told City AM that the firm 'killed' the traditional partnership model a decade ago with that move.