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Ada Ko focuses her practice on cross-border tax, corporate and commercial law. She works primarily with U.S. and foreign corporations, partnerships and individuals on a variety of transactions and reporting requirements, including the tax implications of cross-border business operations, asset/share acquisitions and dispositions, the negotiation of commercial agreements (including supply agreements, lease and license agreements, technology and intellectual property agreements, employment contracts, franchise and management agreements, shareholder agreements, manufacturing, distribution and sales representative agreements), corporate reorganizations and restructuring. In addition, Ada advises foreign governments, foreign pension plans and tax exempt entities and their fiduciaries, with respect to their structuring of U.S. business activities and investments.

A large part of Ada’s practice involves acting as external general counsel advising her clients on a broad range of commercial matters, including utilizing the appropriate business and tax structures. Ada works with clients from around the world in all stages of establishing, acquiring and operating businesses across borders. She works with clients in the formation, implementation and dissolution stages of business in industries ranging from hospitals to fruit growers, and apparel manufacturers to software companies.

Ada is a frequent international speaker on cross-border tax issues.

Representative Engagements

  • Acts as external U.S. general counsel to one of the world’s largest manufacturers of fitness equipment.
  • Acts as external U.S. general counsel to New Zealand’s largest grower, packer, distributor, trader, marketer and exporter of fresh produce by volume, a publicly traded company.
  • Acts as external general counsel to a franchisor of pipfruit in North America.
  • Acts as external general counsel to a U.S. importer/exporter of fresh produce.
  • Provides U.S. tax advice to Canadian provinces and their public sector pension funds investing in the United States.
  • Provides public and private companies advice in structuring their cross border mergers and acquisitions.
  • Provides U.S. tax and corporate advice to a U.S. aviation group in its domestic, international and commercial business transactions.
  • Acted as external general counsel to U.S. software engineering entity that provides testing safety software services to the U.S. government, foreign governments, auto manufacturers and others.
  • Advised foreign governmental postal service on U.S. importation laws.
  • Provided cross-border tax advice to a premier provider of Internet network services and its acquisition of an Australian e-commerce company.
  • Represented several Washington municipalities and companies in state and local tax controversy matters.
  • Represented a Canadian publicly-traded wine conglomerate with the acquisition and structured financing of the second largest wine producer in Washington State.

Professional Activities

  • Licensed U.S. Customs Broker
  • Inter-Pacific Bar Association
  • Canadian Tax Foundation
  • International Fiscal Association
  • King County Bar Association
  • Past-President, Washington State Bar Association, Tax Section
  • Former Adjunct Professor of Law, University of Washington School of Law, Graduate Tax Program (US/Canada Tax Issues)
  • Former Adjunct Professor of Law, Seattle University (Basic Real Estate)

Blog Posts

News & Insights



  • Washington, 1983


University of Washington School of Law, LL.M., Taxation, 1999

Seattle University School of Law, J.D., 1983

University of Washington, B.A., cum laude, 1975

Honors | Recognitions

  • Named as one of The Best Lawyers in America, Tax Law, 2011-2018
  • Martindale-Hubbell International Law Directory: High Ethical Standing, Distinguished - Peer Rated for High Professional Achievement
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