William G. O’Sullivan, CPA, MBA, CGMA

Partner, Orland Park


Bill is a Partner in the Firm’s Client Advisory Services Department and has over 39 years in public accounting. He brings his wealth and depth of experience to middle market, growth oriented and privately owned businesses.  In addition to tax, compilation, review, and accounting services, he also provides general consulting and advisory services that include strategic planning, succession planning, fraud prevention, and cost control.

Bill has served clients in a wide range of industries including professional services, construction, transportation, non-profit, food processing, and manufacturing. His focus is on construction clients such as general and specialty contractors and builders and developers. Bill is a member of the Firm’s Construction Services Group.

Education & certifications

  • B.S.C., Accounting, DePaul University, Chicago
  • MBA, DePaul University, Chicago
  • Licensed Certified Public Accountant
  • Chartered Global Management Accountant
  • Accounting and Business Course Instructor, Moraine Valley community College

Professional & Civic Organizations

  • American Institute of Certified Public Accountants (AICPA)
  • Illinois CPA Society (ICPAS)
  • Chicago Gaelic Park, President
  • Palos Lions Club, Past President
  • ICPAS Construction Contractor Special Interest Group, Past Chair
  • Southwest Suburban Home Builders Association, Member
  • Chicago Southland Chamber of Commerce, Member
  • Irish Fellowship Club of Chicago, Ex-Officio Board Member