Grant Thornton appointed Arla Lach to lead the Chicago market, succeeding Mark Sullivan, who is retiring after more than 14 years with the firm.

Lach, an audit and assurance partner, has been with Grant Thornton for nearly 25 years. Lach and Sullivan are working closely to ensure a seamless transition between now and June 1, 2024. Between Grant Thornton’s Chicago and Downers Grove offices, Lach will lead nearly 1,000 professionals, helping them provide service to the firm’s clients across the country.

Lach assumes this new role at an exciting time for the firm; Grant Thornton will celebrate its 100-year anniversary this summer.

“Arla has been an integral part of Grant Thornton’s growth in Chicago, and she knows how to build and strengthen high-performing teams,” David Platt, central region managing partner of Grant Thornton, said. “It’s extremely rare for businesses to reach 100 years, and it only happens if they have people like her moving the team forward. I know she’ll be a catalyst for even more growth in the years ahead.”

“From her unparalleled client service to her knack for mentoring and motivating our people, Arla has made a tremendous impact on our firm and our Chicago headquarters,” Nichole Jordan, national managing partner of geography at Grant Thornton, said. “I’m looking forward to working alongside her as we drive more growth in the Chicago market and provide truly distinctive experiences to our clients across all industries.”

Lach joined the firm in 1999 and has spent her entire career at Grant Thornton. She has served in a succession of leadership roles, including a two-year appointment as chief of staff to the CEO, during which time she worked alongside the chief executive and other senior leaders to grow the firm’s business.

She also served as the audit practice leader for the Chicago office, and most recently, she was the firm’s Midwest geography leader, overseeing audit work for all clients served by the firm’s teams in Chicago, Minneapolis and Wisconsin. In this role, she helped the firm attain multiple years of record revenues while helping clients successfully navigate the challenges posed by the COVID-19 pandemic and the supply chain crisis.

Her accomplishments in these major leadership roles helped Lach win a 2022 Notable Gen X Leader in Accounting award from Crain’s Chicago Business. Lach’s appointment also makes her the first woman to lead Grant Thornton’s Chicago office.

Lach’s industry experience spans an array of sectors, including manufacturing, distribution, technology, life sciences and professional services. Sullivan has seen firsthand how this industry knowledge benefits Lach’s colleagues and the firm’s clients.

“As part of my Chicagoland leadership team, Arla has spent the last three years epitomizing what it means to be a professional services leader in the new era of our industry,” Sullivan said. “She has the invaluable ability to translate industry knowledge into strong and effective strategies, and just as importantly, she is the kind of compassionate, people-focused leader that professionals love to work with.”

“Mark and our incredible Chicago team have helped Grant Thornton expand our footprint in both Chicago and across the country, and we’re going to continue what we’ve started,” Lach said. “As a lifelong Chicagoan, I take immense pride in providing our city’s businesses a level of service they can’t get anywhere else. That’s why I’m eager to help our talented professionals exceed our clients’ expectations in every way possible.”

Lach earned a bachelor’s degree in accounting from the University of Illinois Urbana-Champaign.