about us

OUR FIRM                                  Timely, Accurate, Personalized

O’Sullivan & Company, PC was established in 1990. Because our firm is relatively small, our clients benefit by receiving timely, accurate and customized service that is beyond comparison. We strive to provide our clients with innovative ideas for tax planning and business opportunities. As your trusted advisors, we are committed to helping you achieve your financial goals through strategic planning and proven expertise. Our goal is to have “no surprises” for our clients.


Daniel T. (Terry) O’Sullivan is the founder and shareholder of O'Sullivan &
Company, P.C. A graduate of Merrimack College with a bachelor's degree in
accountancy, Terry earned his Master of Science in Taxation from Bentley
College and has been a practicing CPA since 1973. He holds the designation of Certified Valuation Analyst and is a member of the American Institute of
Certified Public Accountants (AICPA), the Massachusetts Society of CPAs, and the National Association of Certified Valuation Analysts.

With over 30 years of experience, he oversees the accounting and auditing functions for the firm. He has been involved with various small businesses and is knowledgeable in business planning and taxation. He specializes in business mergers, acquisitions, and sales, real estate development, tax planning, liason for clients in financing arrangements, and valuation assistance.

Terry is very involved in his community and has been on the Boards of many local organizations including Holy Family Hospital, the YMCA and the Haverhill Country Club. He is also an active fund raiser for his alma mater, Central Catholic High School.


Ann MacDonald O’Sullivan is a CPA and shareholder of O’Sullivan & Company, P.C. Ann joined the firm in the summer of 1990. Ann graduated cum laude from Bentley College in 1982 with a bachelor’s degree in accountancy.

Ann puts more than 25 years of taxation experience to work for her clients.
Prior to O'Sullivan & Company, she worked in Boston for the internationally
known firm Price Waterhouse as a tax manager, and at Seidman BDO.

Ann is an active member of the West Newbury community, having served as Selectman for six years and as an at large member of the Community Preservation Act Committee. She has also volunteered as treasurer for various local charitable groups including the Page Elementary PTO and West Newbury Youth League. Ann is the former Treasurer of the Board of Directors of the Pentucket Education Foundation.