It started with Stevie Wonder. The global superstar performed in Finland in 1984, and Ann-Christine Westerlund of Ernst & Young Helsinki was assigned to determine whether Mr. Wonder was obliged to pay taxes in Finland. Ann-Christine studied the U.S.–Finland tax treaty and found it fascinating, so much so that she decided to specialize in U.S.–Nordic taxation during a distinguished 14-year career at Ernst & Young, where she was admitted to the partnership in 1986. A proud Hanken School of Economics alumna, she has built a career spanning more than four decades at the forefront of international taxation.

In 1990, Ann-Christine moved to the United States and founded the Ernst & Young Nordic Tax Desk within the firm's International Tax Department in New York. She led the Desk for three years before co-founding Westerlund & Mousa (later Westmusa) in 1993 together with her husband, acclaimed media executive M.E. Mousa. The firm was built on a simple vision: to provide Nordic companies and individuals with expert U.S. tax, accounting, payroll, and business advisory services. Over the ensuing three decades under Ann-Christine's leadership, Westmusa has grown into a premier U.S. Nordic tax advisory firm, serving a "who's who" of Nordic companies and individuals.

Ann-Christine's deep understanding of both U.S. and Nordic tax systems, combined with her ability to navigate complex cross-border matters, has made her one of the most respected advisors in the field. Fluent in English, Swedish, and Finnish, she works seamlessly with clients across the Nordic region and the United States.

A leading figure in the Nordic community in New York, Ann-Christine has fittingly been described as the "Queen of Networking and Taxes," reflecting her extensive professional network and decades of bringing together Nordic and American businesses. She is an active member of leading Nordic-American professional organizations and the International Taxation Committee of the New York State Society of CPAs. In recognition of her contributions to strengthening ties between Finland and the United States, she was awarded the Knight, First Class, of the Order of the Lion of Finland by the President of Finland, Alexander Stubb.

Outside the office, Ann-Christine enjoys an active lifestyle and is passionate about sports, yoga, and the outdoors. She has completed numerous marathons and half-marathons, including the New York, Helsinki, Stockholm, and Rotterdam Marathons.

For more than a decade, Victor Westerlund has been helping Nordic companies and individuals navigate the U.S tax jungle. Over the years, he has developed extensive experience in cross-border tax planning, compliance, accounting, and business advisory services.

Since joining Westmusa, Victor has worked closely with Ann-Christine Westerlund, advising clients ranging from private individuals and entrepreneurs to multinational companies. Fluent in English, Swedish, and Finnish, he helps clients understand and navigate complex international tax matters.

Based in Raseborg, Finland, Victor works with clients throughout the Nordic countries while maintaining close ties to Westmusa's New York office and regularly visiting the team there. He is also the CEO of Westerlund Tax Oy, an independent Finnish tax advisory firm that assists individuals relocating to or returning to Finland with their Finnish tax obligations. This complements Westmusa's work for Nordic individuals moving to or living in the United States and provides continuity for clients whose tax needs extend across both countries.

Victor holds a Bachelor of Business Administration (BBA) in Finance and Financial Management from Arcada University of Applied Sciences. Outside of work, he enjoys spending time with his family, playing golf, strength training, and running.

Nicholas works with bookkeeping for corporate clients and assists with U.S. tax returns for private individuals. During his two years with Westmusa, he has gained experience supporting a wide range of cross-border tax and accounting engagements, contributing to the day-to-day financial and compliance needs of both businesses and individuals.

Prior to joining Westmusa, Nicholas gained experience in both accounting and marketing roles in Finland, providing him with a well-rounded business perspective and strong organizational skills.

He is currently pursuing a degree in Business Administration at Åbo Akademi University, majoring in Accounting. His bachelor's thesis examined the impact of artificial intelligence on the accounting profession, reflecting his interest in how emerging technologies are shaping the future of finance and accounting.

Fluent in Swedish, English, and Finnish, Nicholas works with clients across the Nordic region and the United States. Outside the office, he enjoys playing golf and experimenting in the kitchen through his passion for cooking.

M.E. Mousa co-founded Westmusa in 1993 and played a central role in building the firm’s presence in the Nordic–US market. With a background in international media and communications, he led Westmusa’s business development and marketing, strengthening partnerships, connecting people, and growing long-term client relationships. 

His vision and support helped establish the firm in New York and contributed to its strong reputation among Nordic companies and individuals. Following retirement, Mousa became an accomplished nature photographer, and his work continues to inspire Westmusa’s visual identity.