Tonneson + Co Merges with Plante Moran

Michigan-based accounting and advisory firm Plante Moran is merging with Tonneson + Co, a top-tier Boston-based firm, effective from July 1. The merger, in line with Plante Moran's East Coast expansion strategy, combines two firms known for their client-centred service philosophy and staff development, with an intent to enhance service capabilities and reach on a global scale.

Plante Moran, a Southfield, Michigan-based accounting and advisory firm with over $1 billion in FY23 revenue, has announced a strategic merger with Boston-based Tonneson + Co, effective July 1. The move underscores Plante Moran’s ongoing expansion along the East Coast and reflects both firms’ dedication to client service and employee development.

Tonneson + Co, one of the top 25 accounting firms in the Boston area, brings to the table a 50-year legacy in audit, tax, and advisory services. With more than 100 professionals and a diversified client base spanning multiple industries and international markets, the firm has cultivated a strong reputation rooted in a client-centric approach. Its team is widely respected for blending technical expertise with long-standing relationship management, aligning closely with Plante Moran’s service philosophy.

Leadership from both firms emphasized the cultural and strategic fit driving the merger. Tonneson CEO Rick Mastrocola noted that the decision to join Plante Moran builds on a foundation of shared independence, mutual respect, and a deep commitment to people and relationships. He highlighted the opportunity for enhanced capabilities without sacrificing the personalized attention that has defined both organizations.

Jason Drake, managing partner at Plante Moran, reiterated the importance of long-term vision in the firm’s growth strategy. With a century-long track record of prioritizing client outcomes and staff development, Plante Moran sees the addition of Tonneson’s team as a natural extension of its values and mission. The merger not only enhances service delivery in the Boston market but also strengthens Plante Moran’s ability to serve clients on a broader, more global scale.

As the July 1 integration approaches, the merger represents a meaningful evolution for both firms, signaling a new chapter of growth anchored in continuity, shared values, and expanded opportunity.

Until next time…

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Plante Moran Strengthens East Coast Footprint with Tonneson + Co Merger

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