Awarded the 2018 Best Newcomer Firm of the Year in Europe by International Tax Review

JC Ceballos

Principal and Founding Member

Juan Carlos ("JC") Ceballos has 17 years of experience in designing, implementing, documenting and defending worldwide transfer pricing policies for the tax and finance departments of multinational companies. JC has been ‘in the trenches’ as an in-house transfer pricing leader for a public company in the Life Sciences industry, and has also worked as an advisor for Deloitte and EY in Mexico, Canada, and the U.S. JC is passionate about using practical transfer pricing strategies to manage global tax risk, in particular, identifying best practices in order to overcome the common challenges that in-house professionals face, such as lack of effective systems/processes, limited resources, inadequate data quality, or insufficient cooperation from other departments. 

JC holds an MBA in Finance from EGADE Business School and a B.S. in Economics from Universidad Autonoma de Guadalajara. He is a frequent speaker and instructor on transfer pricing topics.

JC passions are his two-year-old daughter and four-year-old son, entrepreneurship, traveling,  mountain biking and serving others. He currently resides in Tijuana, Mexico which is located 18 miles away from San Diego, CA. He feels lucky to have the best of two worlds. 


Mark W. Gusho

Principal and Founding Member

Mark Gusho is a Principal and Founding Member of Aptis Global LLC.

For 30 years, Mark has provided international tax advice to multinational companies, including foreign tax credit planning, cash redeployment strategies, local country tax optimization, and tax compliance. He began his career at Arthur Andersen in 1986 and worked in public accounting for a total of 14 years. Mark helped to develop the transfer pricing market in Wisconsin for Arthur Andersen and has since focused on the interplay of international tax and transfer pricing in a company’s global supply chain. Mark has worked for 16 years for various public and private multinational companies, including the manufacturing, medical device, and commodity trading sectors.

Mark earned his Bachelor of Business Administration in Accounting from the University of Wisconsin-Madison. He is a Certified Public Accountant and a member of the American Institute of Certified Public Accountants.

Mark and Susan have been married for 17 years and raised five daughters together. They now focus their attention toward each other and their two dogs. They enjoy cooking, films, and traveling.







John S. MacArthur

Senior Advisor

John S. MacArthur is a Senior Advisor of Aptis Global LLC.

John brings 29 years of international tax experience to the Aptis global strategy team. John served as the Global Private Equity Tax Sector Leader at EY, lead the Asia Pacific International Tax Services practice in Hong Kong, and was the leader of the Pacific North West International Tax Practice. Having augmented his credentials as an Executive Director at Morgan Stanley during his career, John has built a global reputation as a thought leader in taxation of financial institutions, derivatives, and cross-border investment transactions, as well as global private equity and debt capital market financing transactions.

John earned his J.D. at Mitchell Hamline School of Law, where he has had the honor to serve as an Associate Professor during the 2016-2017 academic year, and his B.A. in Economics with Distinction from St. Olaf College. John also earned his Series 7 and Series 48 certifications.

As a world-renowned subject matter expert, John is a frequent speaker on the full array of international tax matters, particularly in the area of financial services.

John is the proud father of three incredible young men who share his passion as an avid outdoorsman along with his sidekick and hunting dog, Luna. The MacArthur roots run nearly 200 years deep in Minneapolis where John currently resides, enabling him to continue his long-term investment as a sponsor of the Boys and Girls Club of Minneapolis and Volunteers of America of Minnesota.


Sofie Stas

Principal and Founding Member

Sofie has 16 years of experience in transfer pricing. She started her career with EY and helped launch the transfer pricing practice within EY Belgium. She participated in global and pan-European transfer pricing and supply chain projects in various sectors such as consumer products, foods and beverages, automotive, biotech, and pharmaceuticals. For more than 10 years, Sofie worked as an in-house transfer pricing expert for one of the largest banks in Belgium and gained extensive experience in the specific transfer pricing issues related to the financial sector, including financing and global trading. During these 10 years, she also gained experience in addressing the various challenges related to the development and implementation of transfer pricing systems within an international organization. Sofie was involved in various transfer pricing audits across Europe and managed the transfer pricing aspects related to business restructuring and post-merger integration.

Sofie is a business engineer from the University of Brussels (Solvay Business School), and she earned a tax degree from the Fiscale Hogeschool Brussels.

Sofie and Manu have been married for 15 years and have a teenage son. They enjoy dining, traveling, and spending quality time with friends and family.






Dale Spiegel

Senior Advisor

As a member of the Aptis Senior Advisor Program (“ASAP”), Dale brings nearly 40 years of expertise to Aptis Global. Having launched his career at Ernst & Young LLP (EY) directly out of law school in 1978, he was promoted to Partner/Principal in 1987. His career was spent working fulltime on international tax planning for US and foreign based multinational companies and their investors, and on foreign related merger and acquisition transactions. In his capacity as a national resource on such transactions he had the privilege of serving a high percentage of EY’s major accounts.

Dale joined EY’s West Coast dedicated mergers and acquisitions practice at its formation in 1998 and remained in the Transaction Advisory Services (TAS) group until his retirement in June 2014. Previously Dale had three tours with EY’s International Tax Services National Office in New York (1978-1982, 1986-1992, and 1995-1998), and tours with EY’s international tax groups in EY’s San Jose technology practice (1992-1995) and EY’s Seattle practice (1982-1986).

Dale has a BA with Honors in Politics from Princeton University (1975), a JD from Cornell School of Law (1978) and an MS in Accounting from New York University’s graduate business school (1980). Dale is admitted to practice before the California and New York Bars.