Grant Thornton US and Ireland complete merger

Grant Thornton Advisors LLC in the U.S. and Grant Thornton Ireland have combined, bringing together two members of the Grant Thornton International network.

The deal was originally announced last October and closed on Friday. It was backed by an investor group led by New Mountain Capital, an investment firm with approximately $55 billion in assets under management. New Mountain Capital acquired a majority stake in the Top 10 Firm last March after previously acquiring a majority stake in another major accounting firm, Citrin Cooperman, in 2021. As is common in PE deals with accounting firms, Grant Thornton split its attest and nonattest sides, naming the nonattest side Grant Thornton Advisors and the attest side Grant Thornton LLP. The audit practice in Ireland will operate under an alternative practice structure similar to Grant Thornton in the U.S. 

The combined firm will include approximately 12,000 professionals with a united Trans-Atlantic advisory and tax practice, as well as independent audit practices. The more than 50 global offices will span the U.S., Ireland and other territories. The new organization will continue to be part of the Grant Thornton International Limited network, which provides access to more than 150 markets globally.

Grant Thornton's firm in the U.S. achieved record annual revenue last year of $2.4 billion with more than 40 offices in the U.S. and India. Grant Thornton Ireland also recently achieved record annual revenue of over €300 million ($333 million).

Grant Thornton Advisors CEO Seth Siegel will continue in his leadership role at the combined firm, while former Grant Thornton Ireland CEO Steve Tennant will become a member of Grant Thornton Advisors' executive committee.

"Today marks a pivotal moment as we create a unique organization within the Grant Thornton network, and a compelling new platform within our industry," Siegel said in a statement Friday. "We will be at the forefront of exceptional quality and differentiated solutions for a growing international client base — offering seamless cross-border collaboration and cutting-edge technologies. This is a transformative step as we become the destination of choice for clients and talent alike."

"This new platform's unmatched talent, comprehensive solutions, and international reach — backed by a commitment to quality — will deliver exceptional results for clients and foster sustainable success for years to come," Tennant said in a statement. "At the same time, we'll become an employer of choice across global markets with a common client-centric culture."

Grant Thornton laid off about 150 employees in the U.S. last November across the advisory, tax and audit businesses after the deal was announced. Its U.K. firm also received private equity investment last November from Cinven, which acquired a majority share of Grant Thornton U.K.