Michigan-based accounting and consulting firm Plante Moran has announced that it has acquired Boston-based accounting and advisory firm, Tonneson + Co, effective July 1, 2025. This strategic combination marks a significant milestone in Plante Moran’s continued expansion along the East Coast and affirms both firms’ commitment to their clients and staff.
Among the largest 25 accounting firms in Boston, Tonneson + Co has a storied 50-year history providing expert audit, tax and advisory services. With a dedicated team of more than 100 professionals and a service footprint that spans multiple industries and international markets, the firm has built its reputation on a client-first philosophy.
“We’re excited to join forces with Plante Moran — a 100-year-old, staunchly independent firm known for its award-winning culture,” said Rick Mastrocola, CEO of Tonneson. “This partnership allows our combined firms to further enhance the capabilities we offer both clients and staff while preserving the unique culture and relationships that have defined Tonneson and Plante Moran for decades.”
Like Plante Moran, Tonneson + Co has been consistently recognized for its emphasis on client service, staff development and community engagement. In 2024, the firm was honored by Accounting Today in its “Best Accounting Firms to Work For” list for the seventh consecutive year.
“For 100 years, Plante Moran has prioritized long-term stability and client success, which has fueled the firm’s steady growth,” said Jason Drake, managing partner of Plante Moran. “Tonneson’s shared values and vision for the future make them an ideal partner. We’re excited to welcome their talented team and expand our presence in Boston.”
SOURCE: Plante Moran
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