Grant Thornton’s $5 billion CBIZ acquisition to create firm with nearly $7.5 billion in revenue

The eighth-largest accounting firm in the nation is being bought by No. 9 in the biggest deal of its kind in more than 25 years, and it will potentially boost the combined entity into the fifth-largest provider of professional services, tax and advisory services.

Grant Thornton announced a definitive agreement to acquire CBIZ in an all-cash $5 billion deal expected to close by year-end.

Grant Thornton, based in Chicago, has been backed by a New York private equity firm, New Mountain Capital, since May 2024. New Mountain Capital will be investing incremental equity to support the transaction. According to industry trade publication Inside Public Accounting’s annual ranking of the largest accounting firms by net revenue, released on July 28, 2026, CBIZ had 2025 revenue of $2.81 billion; Grant Thornton posted $2.46 billion.

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