Insero & Co. CPAs (Insero) and Ciaschi, Dietershagen, Little, Mickelson & Company, LLP (CDLM) have merged as of January 1, 2016. The combined firm will operate under the Insero & Co. name, and employ more than 125 across five locations in Rochester, Ithaca, Corning, Cortland, and Watkins Glen.


“We have worked together for nearly two years and our merger will help us to continue to grow our practice across New York state,” said Nancy Catarisano, who will serve as Managing Partner. “Insero has enjoyed a great reputation for client service and we work with many middle market and family owned businesses in the Rochester area. Together, we are excited to enter Central New York and the Finger Lakes region and create new opportunities for our clients and our staff.”

Insero has repeatedly been recognized nationally as one of the Best Accounting Firms to Work for by Accounting Today and Best Companies Group, and, in 2015, ranked first in the small business category of Rochester’s Top Workplaces by the Democrat and Chronicle and WorkplaceDynamics. The firm is also one of the top 25 employee benefit plan accounting firms in the U.S. based on plan assets audited and provides outsourced staffing solutions to local businesses.

“What excites me about this merger is our combined bench strength and our new focus on expanding our not-for-profit, school district and government audit practice into the Rochester area,” said John Dietershagen, who will serve as Office Managing Partner for the Southern Tier locations. In addition to serving privately held businesses, CDLM currently audits more than 200 local governments, educational entities, not-for-profit organizations and labor organizations throughout Central New York and the Finger Lakes region.

John Dietershagen, CPA

Rochester-based Insero & Co. CPAs is one of the largest accounting and business advisory practices serving New York state. A full-service public accounting firm, Insero provides attest, tax and consulting services to corporations, individuals, government agencies, colleges and universities, not-for-profit organizations and businesses ranging from privately held family businesses to multi-national corporations. These clients represent many industries, including service, manufacturing, distribution, high-tech, telecommunications, education, social services and real estate. For more information, visit