Grant Thornton Advisors LLC in the United States and Grant Thornton Ireland have closed their previously announced transaction to create a global multidisciplinary platform providing audit, advisory and tax services to an international client base.

Grant Thornton Ireland employs approximately 2,700 people in offices in Bermuda, Ireland, Isle of Man and Gibraltar.

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

The new platform of roughly 12,000 professionals will include a united trans-Atlantic advisory and tax practice, as well as independent audit practices.

Its more than 50 global offices will span the US, Ireland and other territories.

The new organisation will continue to be part of the Grant Thornton International Ltd network, which provides access to more than 150 markets globally.

Grant Thornton Advisors’ chief executive, Seth Siegel, will continue in his leadership role and Ireland’s Steve Tennant will become a member of Grant Thornton Advisors’ executive committee.

Mr Siegel said: “Today marks a pivotal moment as we create a unique organisation within the Grant Thornton network, and a compelling new platform within our industry.

“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.”

Mr Tennant added: “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.

“At the same time, we’ll become an employer of choice across global markets with a common client-centric culture.”