William Kambas > Withers Bergman LLP > New York, United States > Lawyer Profile

Withers Bergman LLP
NEW YORK, NY 10022-3505
United States

Work Department

Personal Tax




William 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 wide variety of private and public businesses, including family-owned, start-ups and multi-million dollar enterprises on purely domestic as well as inbound and outbound business transactions, cross-border investments (whether made directly or through investment funds or joint ventures), and qualification for US tax treaty benefits. In particular, he has considerable experience advising non-US persons on the US income and estate tax consequences and tax planning associated with the ownership of US real estate (whether residential or commercial, development, operational, or for personal use).

An integral part of Bill’s work 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.

In addition to numerous speaking engagements, organization memberships and publications, Bill has been featured as a guest lecturer at the Heckerling Institute, the Hellenic Studies Program at Yale University, the Columbia Business School at Columbia University, the University of Connecticut School of Law and the Charles F. Dolan School of Business at Fairfield University. He also was specifically recognized as a “key lawyer” as part of the Withers US International Tax Team ranked by the US Legal 500 2020.


Society of Trust and Estate Practitioners “STEP” (New York), Chair of Communications

International Fiscal Association (Westchester, NY and Connecticut Region), Executive Committee

Skidmore College Annual Fund, President

Saint Barbara Greek Orthodox Church Endowment Fund, Chairman

Hellenic Bar Association of Connecticut

New York State Bar Association

Connecticut Bar Association

American Bar Association


Skidmore College, B.A.

University of Connecticut School of Business, M.B.A.

University of Connecticut School of Law, J.D. (Certificate in Tax)

Lawyer Rankings

United States > Tax > International tax

Withers LLP advises ultra-high-net-worth individuals on international tax holdings. Splitting his time between Connecticut and New York, William Kambas focuses on US tax structuring and tax planning. In Los Angeles, Michael Brophy covers trusts and estates litigation, while Charles Kolstad is an expert in digital asset, income, and estate tax planning. Michelle Graham operates out of San Diego and advises ultra-high-net-worth individuals with US assets. 2021 saw the opening of a new Texas office, lead by cross-border tax expert Kevin Keen, who joined in March from Winstead PC. Additionally, Marsha Laine Dungog was appointed San Francisco office leader in February 2021, and specializes in Canadian and Australian tax, trust, and superannuation matters.

United States > Tax > Not-for-profit (nonprofit and tax exempt organizations)

The tax-exempt practice at Withers Bergman LLP is housed within the firm’s wider private client practice group and excels in domestic and international non-profit work. Led by William Kambas in New York, the team advises cross-border gift-giving, investments and estate planning; recently promoted partner Helen Cheng in San Diego who is ‘excellent’ according to clients, is the key name for this area. Steven Chidester in San Diego represents organizations in IRS audits and handles charitable giving. Co-chair of the practice Michael Brophy  handles estate litigation, from Los Angeles. Other key contacts include Alana Petraske in New York who has a specialty advising charities to attain tax-efficient status both in the US and the UK, and Lawton Leung  in New Haven.