NEW YORK (November 3, 2025) — Frank Agostino, a veteran of the tax bar known for bringing seminal cases that establish favorable law for taxpayers, has joined forces with Kostelanetz LLP, enriching the firm’s already strong reputation as a premier tax controversy and white collar defense boutique.
Joining Frank under the Kostelanetz umbrella are three additional attorneys from Agostino & Associates, Brian Derdowski, Shan Kadkoy, and Byung Hyuk (Billy) Min, as well as Enrolled Agent Michael Wallace. Frank and Brian join as Counsel, while Shan and Billy join as Associates. Frank, Brian, Shan, Billy, and Michael will continue to work out of Hackensack, New Jersey, where Kostelanetz will now have an office.
During his four decades of practicing tax law, Frank has been the driving force behind many successful lawsuits that sought to establish fair tax enforcement principles for taxpayers. Frank has extensive courtroom experience, litigating more than 100 tax cases, several of which created important precedents for taxpayers. For example, Frank defended the taxpayer in a landmark suit, Commissioner v. Zuch, 145 S.Ct. 1707 (2025), in which the U.S. Supreme Court held that the U.S. Tax Court has limited jurisdiction over certain tax enforcement matters. Similarly, in Chai v. Commissioner, 851 F.3d 190 (2d Cir. 2017), Frank helped to establish that the IRS must obtain supervisory approval before imposing penalties in tax deficiency proceedings. In those and other significant cases, Frank’s challenges to government enforcement processes resulted in precedents that have changed the way the IRS and Tax Court do business, while equipping tax lawyers with new arguments with which to defend their clients.
Because of Frank’s stellar reputation in the tax bar, he has been ranked in Chambers in Band 1 for Tax: Fraud Nationwide (USA) and for High Net Worth Private Client: Tax.
“By joining Kostelanetz, Frank and his team mark an important expansion of our firm’s tax controversy practice, pro bono services, and continuing legal education capabilities,” said partner Bryan C. Skarlatos. “Tax enforcement is here to stay, and this combination strengthens our ability to serve our clients at a high level and ensures our firm is positioned as a leader in determining the future of tax compliance and enforcement.”
“I have dedicated my practice to ensuring that everyone who appears before tax authorities gets high-quality representation, whether that is a high-net-worth client with complicated assets and reporting requirements or a lower-income pro bono client who needs assistance navigating the vagaries of the IRS,” said Frank Agostino. “In everything I do, I try to improve the law for all taxpayers and ensure that the government treats my clients with fairness and restraint.”
In addition to Frank’s sophisticated tax controversy practice, his firm’s extensive pro bono activities — including the Taxpayer Assistance Corporation (TAC), one of the largest networks of practitioners representing low-income taxpayers in tax disputes with the government — will augment Kostelanetz’s strong commitment to pro bono representation. In 2023 and 2024, Kostelanetz devoted more than 3,000 hours and more than $2 million in pro bono activities. Frank and his firm have won awards for the breadth of work they have done for low-income and underserved taxpayers. Together, Kostelanetz is excited to be able to add this robust pro bono component to its work.
Kostelanetz and Agostino & Associates are well-known for providing legal and other tax-specific training programs for both government and private practice professionals. By combining these training capabilities, the firm augments its existing reputation as a leading educational resource for tax professionals.
Prior to entering private practice, Frank was an attorney with the IRS District Counsel in Springfield, Illinois, and in Newark, New Jersey. He also served as a Special Assistant United States Attorney, where he primarily prosecuted criminal tax cases. As an adjunct professor, Frank has taught tax controversy at the Seton Hall University W. Paul Stillman School of Business and Rutgers School of Law. He also has served as the co-director of the Rutgers Federal Tax Law Clinic.
Frank is a frequent speaker and author on tax controversy and litigation matters. He serves on the Advisory Board of the Journal of Tax Practice and Procedure, and he is actively involved with the American Bar Association and the New York County Lawyers’ Association.
For nearly 80 years, Kostelanetz LLP has built a global reputation as a law firm of choice for clients facing high-stakes controversies, negotiations with government agencies, and complex domestic and international tax planning decisions. Our attorneys have extensive experience in tax controversy, tax fraud defense, white-collar criminal defense, securities enforcement defense, trust and estate planning, transactional tax planning, and government investigations. We are regularly called upon to handle the most challenging and sensitive matters and internal investigations. Important parts of the firm’s practice also include commercial litigation and government procurement and contracting.
