John Anthony Castro, J.D., LL.M Photo
  • Bio

John Anthony Castro, J.D., LL.M

Managing Partner

John Anthony Castro is the managing partner of Castro & Co. Dr. Castro earned his Master of Laws (LL.M.) in International Taxation from Georgetown University Law Center in Washington, DC. Dr. Castro also earned a Doctor of Jurisprudence (J.D.) from UNM School of Law. Additionally, Dr. Castro is a graduate, alum, and fellow of Harvard Business School. Dr. Castro is an internationally recognized published scholar and author of International Taxation in Plain English, a soon to be published practitioner’s guide for attorneys practicing in the field of international tax and estate planning.

Dr. Castro is listed on each and every return submitted by Castro & Co. and AiTax as a Third-Party Designee, which authorizes him to practice federal tax law in all 50 states as well as the 68 countries with which the U.S. has income and estate tax treaties. In accordance with 5 U.S.C. § 500, generally, and 31 U.S.C. § 330, specifically, Dr. Castro is authorized to practice before the IRS albeit the U.S. Treasury has chosen not to regulate third-party designees listed on federal income tax returns. Nevertheless, Dr. Castro’s activities are authorized by federal law. As such, Dr. Castro is a federal tax practitioner and state bars cannot lawfully regulate his activities.

The general public does not know the difference between a state-licensed attorney that practices state law and the exemption for federal attorneys such as federal tax attorneys and patent attorneys that do not practice state law. Federal practitioners are not required to obtain state licensing because they only interpret and practice under federal laws; not state laws. The Florida Supreme Court articulates it very well in this document: click here (PDF Page 5, Section 11 “Federal Tax Practice”).

As the Florida Supreme Court’s analysis of the U.S. Supreme Court’s decision in Sperry v. Florida (373 U.S. 379, 1963) outlines, the activity of advising on federal tax law and income tax treaties is the “practice of law; it is merely authorized by federal regulation” leaving state bars without jurisdiction. This is what we in the legal profession call the “licensing exemption for federal practitioners.” Federal practitioners do not need to be licensed with a state bar. Moreover, state tax law and estate tax planning are matters ancillary to the federal practice and are also covered. In other words, just as preparing state income tax returns is allowed, our firm’s position is that preparing state trusts are also covered. We understand the issue of state trusts being ancillary to the federal practice is a matter that is not settled law, but we are approaching it in good-faith to establish precedent. We have a positive working relationship with all state bars.

We believe in honesty and transparency and always welcome respectful due diligence from clients and colleagues. If you have any other questions, please do not hesitate to contact our offices.

Contact Our Firm for International Tax Matters

Although Castro & Co. has only four central offices in the United States, Castro & Co. provides legal counsel on international tax and estate planning matters to clients all over the world.

Our firm is primarily known for four major solutions including:

  • Tax exemption for Australian superannuation funds
  • Residency planning for Brazilian nationals to avoid exposure to taxation on worldwide income
  • A 100% acceptance rate for cases submitted pursuant to the Streamlined Filing Compliance Procedures under the Offshore Voluntary Disclosure Program, and
  • Exit tax planning for U.S. citizens wishing to relinquish their passport and long-term green card holders wishing to permanently surrender their residency.

Castro & Co. is looking forward to serving clients worldwide from our offices in Washington DC, Miami, Orlando, and Dallas.

If you would like to schedule an appointment with one of our attorneys, please contact us today by calling (833) 227-8761.


  • International Corporate Tax Planning
  • International Individual Tax Planning
  • International Estate Planning
  • Tax Controversies & Litigation
  • Other Related Litigation


  • Defense & Intelligence
  • Fashion
  • International Trade
  • Manufacturing
  • Pharmaceutical
  • Real Estate
  • Telecommunications


  • Washington DC, U.S. Department of the Treasury


  • O.P.M. Candidate, Harvard Business School
  • LL.M., Georgetown University Law Center
  • J.D., UNM School of Law
  • B.A., Texas A&M International University
Let's Chat, It's Free.

Contact Our Team Today

Complete our form below or call us at (833) 227-8761.

  • Please enter your first name.
  • Please enter your last name.
  • Please enter your phone number.
    This isn't a valid phone number.
  • Please enter your email address.
    This isn't a valid email address.
  • Please make a selection.
  • Please enter a message.
  • By submitting, you agree to be contacted about your request & other information using automated technology. Message frequency varies. Msg & data rates may apply. Text STOP to cancel. Acceptable Use Policy