News release

RSM Enhances Its Nonprofit Practice by Joining Forces with the U.S. and Canadian Operations of C Systems and Confluence Global

Aug 05, 2021

Kimberly Bartok, Enterprise Public Relations Leader,, 212.372.1239
Andreia DeVries, Enterprise Public Relations Manager,, 919.645.6821
for media use only 

RSM Enhances Its Nonprofit Practice by Joining Forces with the U.S. and Canadian Operations of C Systems and Confluence Global

CHICAGO – (August 5, 2021) – RSM US LLP (“RSM”) – the nation’s leading provider of audit, tax and consulting services focused on the middle market – announced today that the leaders and staff of the U.S. and Canadian operations of C Systems, a nonprofit technology services and association management systems (AMS) consulting firm, and Confluence Global, a Salesforce consulting partner, will join RSM. The firms have signed a definitive agreement for RSM to acquire substantially all of the assets of C Systems, LLC,* C Systems Canada, LLC, and Confluence Global, LLC. The transaction is expected to close on Sept. 1, 2021, subject to certain terms and conditions.

The combination strengthens RSM’s foothold in the nonprofit industry by reinforcing the firm’s multi-solution AMS capabilities through the expansion of its iMIS Engagement Management System software team and RSM’s leading Salesforce practice. The platforms support constituent relationship management, content management, e-commerce and e-marketing functionality for associations, nonprofits and member-based organizations. As part of its broad audit, tax and consulting services for associations, RSM now offers software solutions and implementation services for iMIS, Microsoft Dynamics, NetSuite, and Nimble AMS, which is built on the Salesforce platform.

Upon the close of the transaction, Lee Hornstein, CEO of the Edison, N.J.-based C Systems, and Craig Dellorso, CEO of Washington, D.C.-based Confluence Global, and their teams of professionals will join RSM. Hornstein and the C Systems team bring advanced expertise in iMIS platform consulting and implementation services, refined over 20 years since the firm’s inception and earning C Systems the Authorized iMIS Solution Provider of the Year award four times. Dellorso and the Confluence Global team bring deep experience providing technology solutions, including specialized knowledge in supporting Nimble AMS.

“RSM powers its industry-focused strategy with leading consulting solutions to serve our clients’ needs,” said Brian Becker, consulting leader for RSM US LLP. “The outstanding C Systems and Confluence Global teams will enhance our ability to help associations and nonprofit organizations leverage technology to meet the unique opportunities and challenges they face.”

“Joining RSM is a crucial next step in our firm’s growth strategy and an exciting step forward for our people and our clients,” said Hornstein. “Our firms are eager to bring together our experience, knowledge and industry relationships to help our combined team expand our service to the nonprofit sector.”

“We are thrilled to join a firm that shares our passion for the industries we serve and that is committed to helping clients bolster their success through technology,” said Dellorso. “Our shared culture and values will help ensure successful collaboration leading to even greater innovative solutions for our clients and growth for our people.”

Hornstein will join RSM as a consulting principal and Dellorso will join RSM as a consulting director; their teams will also transition to RSM upon closing.

The transaction comes on the heels of RSM’s 2019 acquisition of the assets of Washington, D.C.-based Tate & Tryon, P.C., a leading audit, tax, outsourced accounting and technology services firm focused exclusively on serving nonprofit organizations, and the firm’s 2020 acquisition of the assets of MondayCall LLC, a Salesforce consulting partner.

*C Systems’ U.K. operations and certain specialized products will be continued by C Systems Global, Ltd., independent from RSM, under the leadership of Jeremy Wilson with a new brand to be established on or before Sept. 1.


RSM is the leading provider of professional services to the middle market. The clients we serve are the engine of global commerce and economic growth, and we are focused on developing leading professionals and services to meet their evolving needs in today’s ever-changing business landscape. Our purpose is to instill confidence in a world of change, empowering our clients and people to realize their full potential.

RSM US LLP is the U.S. member of RSM International, a global network of independent assurance, tax and consulting firms with 64,000 people in 120 countries. For more information, visit, like us on Facebook, follow us on X and/or connect with us on LinkedIn.