Area of Focus

Phyllis Deiso

Partner, National SEC Practice Leader

About Phyllis

Phyllis Deiso is an SEC-designated assurance partner and the national SEC practice leader for RSM US LLP. Known as an accomplished, energetic leader within the firm, she is a former member of the RSM US LLP Board of Directors and served as chair of the risk oversight and governance board committees.


As national SEC practice leader, Phyllis works strategically with the firm’s five regional SEC leaders to ensure the firm is serving all SEC registrant clients with close partner attention, requisite experience, proper business acumen and deep technical expertise. With more than 30 years of experience in public accounting, Phyllis’ success can be attributed to her extensive SEC financial reporting knowledge as well as her ability to communicate with, and provide timely service, to her clients. She always has found her engagement with clients intellectually stimulating, and the part of her job she enjoys the most.

Throughout her career, Phyllis has served and continues to serve large multinational SEC clients, including those that conducted multibillion-dollar carve-out and spin-off transactions, mergers, acquisitions and initial public offerings. She has served a number of registrants in various industries, including concentrations in the broadcast, manufacturing, transportation and distribution industries.

Phyllis has held many leadership roles within RSM. During her term on the firm’s board of directors, she helped guide the firm through a pivotal time as it was rebranding. Her professional development work includes mentoring and coaching within the firm to help raise up the next generation of RSM leaders. A relationship builder, she is known for her ability to make personal connections with clients and colleagues on a one-on-one basis.

Prior to RSM, Phyllis was with a Big Four accounting firm, having served primarily in its SEC practice and as a technical resource for accounting, auditing and SEC reporting matters. She was drawn to RSM in 2006 because of the manner in which the firm serves clients and the opportunities she saw to affect the firm’s SEC practice.

In 2015, Phyllis led a team that was named by RSM as “team of the year” and in 2009, she was a finalist for the firm’s “partner of the year” award. She has been recognized by the National Association of Corporate Directors for the past seven years as a Directorship 100 honoree for her outstanding work in the area of corporate governance. She is a frequent speaker and author on governance topics affecting SEC registrants, ranging from regulatory and reporting issues to risk management matters.

Outside of work, Phyllis enjoys spending time with family, including her children and grandchildren. She loves to entertain in her home, making guests feel welcome with an excess of fun, décor and delicious meat prepared on her wood pellet smoker.

Professional affiliations and designations

  • Certified public accountant
  • American Institute of Certified Public Accountants
  • Florida Institute of CPAs


  • Bachelor of Business Administration, accounting (summa cum laude), Florida Atlantic University