One Firm | One Team | One Goal
Turnerstone. is a full-service public accounting firm specializing in tax compliance and planning for high net worth individuals and integrated accounting, tax and business advisory for closely-held businesses. Our professionals are tenured in providing consistent value to clients by committing to the highest standards and leaving ‘No Stone Left Unturned’.
Leadership Team
Walter McMahon
President
Ross Collins
Senior Tax Advisor
Mary-Claire Corcoran
Director
Judy Morgan
Director
Timothy Mehl
Assistant Director
Marian Borzelleca
Senior Manager
Samantha T. McMahon
Executive Administrator
Joanna T. Kelly
Marketing Coordinator
Walter McMahon
President
Walter joined the firm in June 2021 in connection with the restructuring of RRC Accounting Services, LLC to Turnerstone. LLC. He brings over 14 years of audit, accounting, tax and business consulting experience from his career with PricewaterhouseCoopers LLP, where he serviced public and non-public companies as a Director in the Financial Services sector of the Assurance practice in Philadelphia. His professional specialties include attestation and business advisory services, including U.S. GAAP, SEC, Sarbanes-Oxley and ERISA compliance requirements, as well as individual, business, estate and trust tax compliance and planning, and small business bookkeeping and general accounting.
Walter graduated maxima cum laude with a B.S. in Business Administration from La Salle University. He is a certified public accountant in the Commonwealth of Pennsylvania, and a member of the American Institute of Certified Public Accountants and Pennsylvania Institute of Certified Public Accountants.
He is also a member of the Board and Treasurer of Discover Haverford, a nonprofit organization that facilitates government, businesses, commercial property owners and residents working together to promote economic growth throughout Haverford Township.
Walter, his wife Samantha (below), and their two sons reside in Havertown, Pennsylvania. He enjoys playing golf, and vacationing with family and friends.
Ross Collins
Senior Tax Advisor
Ross has over 48 years of experience in individual, business, estate and trust tax compliance and planning. He has also specialized in complex business purchase and sale transactions, as well as financial and accounting systems for businesses and nonprofit organizations. Ross began his career in 1974 at Price Waterhouse. Following 12 years with Price Waterhouse, Ross worked as the Chief Financial Officer of several privately held businesses. In 2000, Ross returned to public accounting as a Partner at Tax Counsellors of Bryn Mawr, LLC, and in 2012, founded RRC Accounting Services, LLC.
Ross graduated with a B.A. in Economics from Ohio Wesleyan University and earned his Masters in Business Administration from the Wharton School of the University of Pennsylvania. He has been a certified public accountant in the Commonwealth of Pennsylvania since 1974, and is a member of the American Institute of Certified Public Accountants and Pennsylvania Institute of Certified Public Accountants.
Ross and his wife Diane reside in Wayne, Pennsylvania. He enjoys playing golf, and spending time with his two grown sons.
Mary-Claire Corcoran
Director
Mary-Claire joined the firm in February 2015. She has over 40 years of experience in individual, business, estate and trust tax compliance and planning, and small business bookkeeping and general accounting.
Mary-Claire graduated with honors with a B.A. in Accounting from Rutgers University. She is a certified public accountant in the Commonwealth of Pennsylvania, and a member of the Accounting & Financial Women’s Alliance where she serves as Treasurer for the Philadelphia Chapter. She is also a member of the Board of Northwoods Community Association.
Mary-Claire and her husband Mike reside in Glenside, Pennsylvania. They enjoy traveling and spending time with family and friends, especially their children and grandchildren.
Judy Morgan
Director
Judy joined the firm in December 2008. She has over 30 years of experience in individual, business, estate and trust tax compliance and planning, and small business bookkeeping and general accounting.
Judy graduated with recognition with a B.S. in Business Administration from Cabrini University. She is a certified public accountant in the Commonwealth of Pennsylvania.
Judy and her husband Ron reside in Millville, Delaware. She enjoys traveling with friends, reading, walking for exercise, yoga, spoiling 5 grandchildren, entertaining and spending time with Ron.
Timothy Mehl
Assistant Director
Tim joined the firm in November 2023. He brings over 16 years of tax, accounting, and business consulting experience from his career with various professional services firms. Tim began his professional career in public accounting at KPMG Philadelphia, and then entered the private industry with SAP America in Newtown Square, Pennsylvania, where he worked in the tax department performing corporate compliance and tax-related project management. Following SAP America, Tim returned to public accounting at Gunnip & Company, a regional firm in Greenville, Delaware, and most recently, BDO USA Philadelphia, where he focused on corporate, partnership, estate, trust and high-net worth individual tax services. His professional specialties include business, individual, estate and trust tax compliance and planning, and he is an expert in small business bookkeeping and general accounting.
Tim graduated magna cum laude with a B.S. in Accounting from Penn State University. He is a certified public accountant in the Commonwealth of Pennsylvania, and a member of the American Institute of Certified Public Accountants and Pennsylvania Institute of Certified Public Accountants.
Tim resides in Glen Mills, Pennsylvania. He enjoys playing piano and golf. He also enjoys vacationing and dining out with his family and close friends.
Marian Borzelleca
Senior Manager
Marian joined the firm in January 2019. She has over 40 years of experience in individual, business, estate and trust tax compliance and planning, and small business bookkeeping and general accounting.
Marian graduated with recognition with a B.B.A in Accounting from the University of Notre Dame, and earned her Masters in Business Administration from Philadelphia University. She is a certified public accountant in the Commonwealth of Pennsylvania, and a member of the American Society of Women Accountants where she serves as the Scholarship Chairperson. She is also a member of the Board of Belvoir Woods Home Owner’s Association where she serves as Treasurer.
Marian resides in Plymouth Meeting, Pennsylvania and St. Petersburg, Florida. She enjoys traveling and spending time with friends and family.
Samantha Turner McMahon
Executive Administrator
Samantha leads the professional administration of the firm. She currently serves as a Deployment Consultant Manager at PricewaterhouseCoopers LLP, specializing in sourcing, staffing and professional development for national advisory groups. Prior to transitioning to talent management, Samantha conducted audits of public and non-public companies as an Associate in the Philadelphia office.
Samantha graduated with recognition with a B.B.A. in Accounting from Temple University.
Samantha, her husband Walter (above), and their two sons reside in Havertown, Pennsylvania. She enjoys trying new restaurants, spending time with family and friends, and getting caught up on the latest shows.
Joanna Turner Kelly
Marketing Coordinator
Joanna leads the marketing and community outreach strategy of the firm. She previously served as a Registration & Events Manager for a large travel management company and as a Meeting Coordinator for a large credit card company. She is the Head Coach for the Haverford High School cheerleading team, providing mentorship and guidance to youth in the community since 2008.
Joanna graduated with recognition with a B.A. in Strategic Communication from Temple University.
Joanna, her husband Kevin, and their three children reside in Havertown, Pennsylvania. She enjoys networking in the community, spending time with family and friends, and winning cheer competitions.