Grant Thornton to acquire Stax

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Grant Thornton Advisors to add top diligence and value-creation provider Stax
Together, they will serve almost 70% of the U.S.-based Private Equity International 300

CHICAGO and BOSTON, August 19, 2025 — Grant Thornton Advisors LLC (Grant Thornton Advisors) today announced it will acquire Stax, a leading strategy consulting firm specialising in commercial due diligence, value creation and exit-planning services for private equity (PE) firms, as well as their portfolio companies and advisers.

Headquartered in Boston with a presence across key financial markets, Stax provides buy- and sell-side diligence and planning for merger and acquisition (M&A) activities, while delivering clients with growth strategies and value-creation initiatives. The firm’s data-driven approach taps into leading AI and advanced intelligence to deliver actionable insights and proven successes for its clients.

The three-decade-old firm has grown rapidly in recent years, while maintaining high client-retention rates and lengthy stakeholder relationships. It serves many of the leading players in large-cap and middle-market PE, alternative investments and investment banking.

The acquisition will elevate U.S.-headquartered Grant Thornton Advisors’ market-leading transaction advisory team by enhancing the breadth and depth of its M&A capabilities. The practice currently has more than 600 PE relationships, including 60% of the top 10 global PE firms by total equity, and more than 1,600 sponsor-backed clients. The deal with Stax further expands Grant Thornton Advisors’ commercial-diligence offerings and adds Stax’s seasoned transaction-consulting leadership team and entrepreneurial energy. Together, the two firms will service almost 70% of the U.S.-based Private Equity International 300.

The transaction grows the multinational, multi-disciplinary platform that Grant Thornton Advisors established in January 2025. To date, it has announced transactions with several 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 announced a deal last month to acquire Auxis, a U.S. based leader and pioneer in outsourcing and business-modernisation services.

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.

“With this bold move, we’re taking our platform to new heights — combining Stax’s top-tier talent with our own industry-leading professionals, while broadening our offerings and further elevating our tech capabilities,” said Jim Peko, CEO of Grant Thornton Advisors.

“Stax has a decades-long legacy delivering transformative value to clients — similar to our own 100-year history. Together, we will generate bold results for a PE client base stretching from the Americas across Europe to the Middle East.”

“PE firms today don’t just want an adviser; they want a partner with agility, intelligence and scale,” said Tom Puthiyamadam, managing partner for Advisory Services at Grant Thornton Advisors. “By adding Stax, we’re combining trust with data-driven precision to unlock strategic value at every stage of the investment lifecycle. This is more than an expansion — it’s a leap forward in delivering outcomes for PE and corporate clients.”

According to Jayson Traxler, CEO of Stax:

“We are proud to have built a 30-year reputation for excellent client service, unique tech-enabled solutions and impressive growth. As part of Grant Thornton Advisors, those characteristics will endure — but with far greater scale, speed and amplification of our impact. We will be empowered to build on our unique strengths and insights, for the benefit of the leading PE firms, portfolio companies and investment banks.”

Stax’s approximately 300 team members will join Grant Thornton Advisors when the transaction closes, which is expected to take place in 2025, subject to standard closing conditions.

Andre Moura and Nikhil Devulapalli, managing directors at New Mountain Capital, said:

“Stax’s world-class commercial diligence and value-creation capabilities are highly complementary to Grant Thornton Advisors’ scaled transaction advisory offering. The addition of Stax enables Grant Thornton to better serve its clients as they contemplate and execute on major investment decisions and operating initiatives. We are proud to continue supporting Grant Thornton as the firm grows and broadens its capabilities.”

In addition to transaction-related services, Grant Thornton Advisors provides a range of services centered on strategy, transformation and operations. These include offerings across technology, finance, operations, sales and marketing, data, AI, cybersecurity and risk. It also provides a complete slate of tax services.

Clearsight Advisors, Inc. and Harris Williams served as financial advisers to Grant Thornton Advisors — and its legal adviser was Simpson Thacher & Bartlett LLP. William Blair served as financial adviser to Stax. Jones Day served as legal adviser to Stax. Stout served as sell-side financial diligence and tax adviser to Stax.

About Grant Thornton

Grant Thornton delivers professional services in the US through two specialised 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. The platform offers a premier advisory and tax practice, as well as independent audit practices. With almost 60 offices, the platform delivers a singular client experience that includes enhanced solutions and capabilities, backed by powerful technologies and a roster of almost 13,000 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 specialising 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

Richard Gillan Richard leads Grant Thornton’s Northern Ireland practice and has driven a ten-fold revenue increase over the past decade. With extensive leadership experience across advisory, tax, and international operations, he also serves on the US Tax Executive Leadership team. View Profile
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

Copy text of article

Press Release

Grant Thornton Advisors to add consulting firm Stax

19 Aug 2025

Grant Thornton Advisors to add top diligence and value-creation provider Stax
Together, they will serve almost 70% of the U.S.-based Private Equity International 300

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.

“With this bold move, we’re taking our platform to new heights — combining Stax’s top-tier talent with our own industry-leading professionals, while broadening our offerings and further elevating our tech capabilities,” said Jim Peko, CEO of Grant Thornton Advisors.

“Stax has a decades-long legacy delivering transformative value to clients — similar to our own 100-year history. Together, we will generate bold results for a PE client base stretching from the Americas across Europe to the Middle East.”

“PE firms today don’t just want an adviser; they want a partner with agility, intelligence and scale,” said Tom Puthiyamadam, managing partner for Advisory Services at Grant Thornton Advisors. “By adding Stax, we’re combining trust with data-driven precision to unlock strategic value at every stage of the investment lifecycle. This is more than an expansion — it’s a leap forward in delivering outcomes for PE and corporate clients.”

According to Jayson Traxler, CEO of Stax:

“We are proud to have built a 30-year reputation for excellent client service, unique tech-enabled solutions and impressive growth. As part of Grant Thornton Advisors, those characteristics will endure — but with far greater scale, speed and amplification of our impact. We will be empowered to build on our unique strengths and insights, for the benefit of the leading PE firms, portfolio companies and investment banks.”

Stax’s approximately 300 team members will join Grant Thornton Advisors when the transaction closes, which is expected to take place in 2025, subject to standard closing conditions.

Andre Moura and Nikhil Devulapalli, managing directors at New Mountain Capital, said:

“Stax’s world-class commercial diligence and value-creation capabilities are highly complementary to Grant Thornton Advisors’ scaled transaction advisory offering. The addition of Stax enables Grant Thornton to better serve its clients as they contemplate and execute on major investment decisions and operating initiatives. We are proud to continue supporting Grant Thornton as the firm grows and broadens its capabilities.”

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

Richard Gillan

Richard leads Grant Thornton’s Northern Ireland practice and has driven a ten-fold revenue increase over the past decade. With extensive leadership experience across advisory, tax, and international operations, he also serves on the US Tax Executive Leadership team.

View Profile

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