Southfield, Mich., and Boston, Mass., June 9, 2025 — Plante Moran, one of the nation’s largest audit, tax, consulting and wealth management firms, announced that Boston-based accounting and advisory firm, Tonneson + Co, will join the firm, 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 is 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.”
Since its founding in 1924, Plante Moran has grown from a sole accounting practitioner in a Detroit office to a billion-dollar firm with nearly 4,000 professionals serving clients around the globe. Throughout this growth, the firm has stayed true to the values, principles and culture that’ve contributed to its many years of success.
About Plante Moran
Plante Moran is among the nation’s largest audit, tax, consulting, and wealth management firms and provides a full line of services to organizations in the following industries: manufacturing and distribution, financial services, service, healthcare, private equity, public sector, real estate, construction, and energy. Throughout the firm’s 100 years in business, Plante Moran has grown to a staff of nearly 4,000 professionals throughout the United States with international offices in Shanghai, China; Mumbai, India; Tokyo, Japan; and Monterrey, Mexico. Plante Moran has been recognized by a number of organizations, including Fortune magazine, as one of the country’s best places to work. For more information, visit plantemoran.com.
About Tonneson + CO
Tonneson + Co is a full‑service accounting, tax, and advisory firm headquartered in Wakefield, Mass. For more than 50 years, the firm has delivered personalized and trusted advisory services to privately held businesses, individuals, and nonprofits — not only regionally in the Boston area but also across national and global markets. Learn more about their client‑centered approach and extensive service expertise by visiting tonneson.com.
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