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Mark O’Reilly, CPA

Partner

Top 5 Things to Know About Mark

  • Advises closely held businesses on tax, assurance, and growth strategies
  • Brings industry experience across construction, manufacturing, and real estate
  • Helps business owners connect financial data to better decisions
  • Combines technical expertise with a practical, business-minded perspective
  • Known for listening first and providing thoughtful, long-term guidance

Mark O’Reilly works closely with business owners, helping them navigate financial decisions with clarity and confidence. He provides tax and assurance services to closely held businesses and their owners, using financial information not only to meet compliance requirements but also to support stronger decision-making, risk management, and long-term growth.

His experience spans a variety of industries, including construction, manufacturing, real estate, professional services, and wholesale and distribution. Mark began his public accounting career in audit, gaining valuable insight into the operational and financial challenges organizations face. Over time, he developed a broader advisory focus, helping clients understand how financial decisions affect both their businesses and personal objectives. Whether evaluating profitability, pricing, operational efficiency, or long-term planning opportunities, Mark helps clients see beyond the numbers and focus on what drives sustainable success.

Clients value Mark’s practical perspective, thoughtful guidance, and ability to connect technical accounting and tax matters to the realities of running a business.

  • Tax Planning & Compliance
  • Assurance Services
  • Closely Held Businesses
  • Construction Industry Services
  • Real Estate Services
  • Business Advisory Services

  • Certified Public Accountant (CPA)

  • American Institute of Certified Public Accountants (AICPA)
  • New England Society of CPAs
  • Finance Committee Member, Local Church
Outside of Work

Outside of work, Mark enjoys spending time with his wife, three children, two sons-in-law, and grandchild. Family is at the center of his life, and he values every opportunity to be together. He is also a devoted Boston Bruins fan and can often be found either watching a game or cheering on the team in person at the arena.

Ready to experience the difference?

Walter Shuffain is the brand name under which Walter Shuffain Advisors Inc. and WS CPAs P.C. provide professional services. Walter Shuffain Advisors Inc. and WS CPAs PC practice in an alternative practice structure in accordance with the AICPA Code of Professional Conduct and applicable law, regulations and professional standards. WS CPAs PC is a licensed independent CPA firm that provides attest services to its clients. Walter Shuffain Advisors Inc. and its subsidiary entities, which are not licensed CPA firms, provide tax, advisory, and other non-attest services to its clients. The entities are independently owned and governed and are not liable for the services provided by any other entity providing the services under the Walter Shuffain brand. Our use of the terms “our firm” and “we” and “us” and terms of similar import, denote the alternative practice structure conducted by WS CPAs PC and Walter Shuffain Advisors Inc.
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