Family Office Set-up with Ivan Sacks, William Kambas and David Guin

Bill is a partner in, and the Regional Division Leader of, the US Private Client and Tax team at Withers Worldwide.

He focuses on tax planning for multi-national and multi-state personal, active business, and investment activities, with a particular emphasis on tax structuring and choice of business entity for US and non-US business owners and investors.

Bill has represented a variety of private and public interests, including family-owned, start-up, and multi-million dollar enterprises on purely domestic as well as inbound and outbound business transactions and cross-border investments (whether made directly or through investment funds or joint ventures). In particular, he has considerable experience advising on tax planning for US real estate investments (whether residential or commercial, development, operational, or for personal use). An integral part of Bill’s practice involves assisting families and/or their family offices with the formation, management, and/or periodic evaluation of multinational and/or multi-generational centralized control and management structures, such as family offices and private trust companies.


Bill has participated in numerous speaking engagements, industry memberships, and publications. For example, Bill has been a guest lecturer at the Heckerling Institute, the Hellenic Studies Program at Yale University, the Columbia Business School’s Family Business Program at Columbia University, the University of Connecticut School of Law, and the Charles F. Dolan School of Business at Fairfield University, as well as with the International Fiscal Association, American Bar Association, and the Society of Trusts and Estates Practitioners.


Bill has been recognized by a number of industry groups, including as one of the Top 100 Family Influences by Family Capital Media; as a Fellow of the American Bar Foundation; as a “key lawyer” by The Legal 500 US in the area of international tax; as one of the Best Lawyers in the US for the years of 2021, 2020, 2019, and 2018; and as one of the Connecticut Law Tribune’s New England Trailblazers for 2019.

Ivan is a partner in the private client and tax team at Withers Worldwide.

He is a private client lawyer and trusted advisor to international and domestic families and family offices. Ivan heads the Withers Families and Family Office group, is a member of the firm’s Latin American and Asia-Pacific groups, and was also global chairperson of Withersworldwide from July 2013 to July 2019.

Both in the US and in an international context, he counsels families and entrepreneurs on the structuring of their closely held business interests, family offices and charitable foundations, the design and administration of trusts and estates, and comprehensive risk management, governance, and succession planning. He also frequently advises banks and trust companies on fiduciary matters.


Ivan is admitted to the bar of the State of New York and the Federal District Court for the Southern District of New York. He graduated from Columbia Law School, where he was a Harlan Fiske Stone Scholar, a Charles Evans Hughes Fellow, and Editor-in-Chief of the Columbia Human Rights Law Review. He is an active member of several bar associations and speaks frequently on topics related to wealth planning.

He is the global head of Withers Pro Bono programs and serves as a director or other fiduciary for a number of private enterprises, trusts, and charitable organizations. Among publicly acknowledged roles, he is Chairman of the Jose Limon Dance Foundation, Chairman of the International Patrons of the Duomo, and Trustee of the Brugnaro Blind Trust for the Mayor of Venice, Luigi Brugnaro.


Ivan is listed in America’s Best Lawyers, New York Super Lawyers, Legal Week’s Private Client Global Elite, Chambers and Partners, and Citywealth Leaders Lists, among others.

David is a partner in the corporate team Withers Worldwide.

He leads the corporate practice teams in the US. He integrates the knowledge he has gained in representing public companies, fund managers, and investment advisers with his experience in representing family and closely-held enterprises and entrepreneurs.

David has extensive experience advising clients on a range of issues governed by the US Securities Laws and other regulatory matters such as the rules of various self-regulatory organizations.


He devotes a significant amount of time to advising high net worth domestic and international individuals, families, family offices, and their advisors about their obligations under US securities laws, including the acquisition and disposition of public and private securities, beneficial ownership reporting obligations, and the applicability of the US Investment Advisers Act and US Investment Company Act to their investment activities.

David represents hedge funds and investment partnerships with respect to fund formation matters, preparation of fund formation and offering documents, transaction structuring and compliance issues.


He has represented numerous companies in the acquisition and disposition of businesses and business segments and all types of public and private financing transactions.


David also acts as general counsel to many of his clients, advising on governance and fiduciary matters and a wide range of commercial transactions from employment matters to intellectual property licensing.


David is a Member of the Board of Trustees and Counsel to the Museum of the City of New York.

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