Grant Thornton closes deal with Stax

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CHICAGO and BOSTON, September 23, 2025 — Grant Thornton Advisors LLC (Grant Thornton Advisors) has closed its transaction to acquire Stax, a leading strategy consulting firm specializing in commercial due diligence, value creation and exit-planning services for private equity (PE) firms, as well as their portfolio companies and advisers.

The transaction, which was previously announced on August 19, adds Stax’s approximately 300 team members to the Grant Thornton Advisors multinational platform, stretching from the Americas across Europe to the Middle East.

The acquisition elevates U.S.-headquartered Grant Thornton Advisors’ market-leading transaction advisory team by enhancing the breadth and depth of its M&A capabilities. Together, Stax and Grant Thornton Advisors now service almost 70% of the U.S.-based Private Equity International 300.

Three-decade-old Stax has grown rapidly in recent years, while maintaining high client-retention rates and lengthy stakeholder relationships. Its strength comes from serving many of the leading players in large-cap and middle-market PE, alternative investments and investment banking.

Grant Thornton Advisors established its multinational platform in January 2025. To date, transactions have been announced with several full-service accounting and consulting firms to join the platform, including those in Ireland, the UAE, Switzerland/Liechtenstein, the Netherlands, Luxembourg, the Cayman Islands and the Channel Islands. Additionally, Grant Thornton Advisors recently acquired Auxis, a U.S.-based leader and pioneer in outsourcing and business modernization services — powered by AI and automation.

The platform is backed by an investor group led by New Mountain Capital, a growth-oriented investment firm with approximately $55 billion in assets under management.

You can read more about how Grant Thornton Advisors is joining forces with Stax in the August 19 press release announcing the transaction.

About Grant Thornton

Grant Thornton delivers professional services in the US through two specialized entities: Grant Thornton LLP, a licensed, certified public accounting (CPA) firm that provides audit and assurance services ― and Grant Thornton Advisors LLC (not a licensed CPA firm), which exclusively provides non-attest offerings, including tax and advisory services.

In January 2025, Grant Thornton Advisors LLC formed a multinational, multidisciplinary platform with Grant Thornton Ireland. The platform offers a premier advisory and tax practice, as well as independent audit practices. With almost 60 offices across three continents — including the U.S., Ireland, the UAE and other territories — the platform delivers a singular client experience that includes enhanced solutions and capabilities, backed by powerful technologies and a roster of approximately 13,500 quality-driven professionals enjoying exceptional career-growth opportunities and a distinctive cross-border culture.

Grant Thornton is part of the Grant Thornton International Limited network, which provides access to its member firms in more than 150 global markets.

Grant Thornton LLP, Grant Thornton Advisors LLC and their respective subsidiaries operate as an alternative practice structure (APS). The APS conforms with applicable laws, regulations and professional standards, including those from the American Institute of Certified Public Accountants.

“Grant Thornton” refers to the brand under which the member firms in the Grant Thornton International Ltd (GTIL) network provide services to their clients and/or refers to one or more member firms. Grant Thornton LLP and Grant Thornton Advisors LLC serve as the U.S. member firms of the GTIL network. GTIL and its member firms are not a worldwide partnership and all member firms are separate legal entities. Member firms deliver all services; GTIL does not provide services to clients.

About Stax

Stax is a global strategy consulting firm specializing in commercial due diligence, value creation, and exit planning for private equity firms, PE-backed companies, hedge funds, and investment banks across a broad range of industries including software/technology, industrials, business services, healthcare, consumer, and the events ecosystem. The firm partners with clients to provide data-driven, actionable insights designed to drive growth, enhance profits, increase value, and make better investment decisions.

Experts / Authors

Stephen Tennant Stephen is the managing partner of Grant Thornton Ireland and previously led the firm’s financial services advisory practice. He has extensive experience in delivering practical solutions to regulatory challenges faced by global financial institutions. View Profile

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Press release

Grant Thornton closes deal with diligence and value-creation provider Stax

23 Sep 2025

The platform is backed by an investor group led by New Mountain Capital, a growth-oriented investment firm with approximately $55 billion in assets under management.

You can read more about how Grant Thornton Advisors is joining forces with Stax in the August 19 press release announcing the transaction.

About Grant Thornton

Grant Thornton is part of the Grant Thornton International Limited network, which provides access to its member firms in more than 150 global markets.

About Stax

Experts / Authors

Stephen Tennant

Stephen is the managing partner of Grant Thornton Ireland and previously led the firm’s financial services advisory practice. He has extensive experience in delivering practical solutions to regulatory challenges faced by global financial institutions.

View Profile