1946: Boris Kostelanetz and Howard F. Corcoran leave the U.S. Attorney’s Office in Manhattan to found the firm, Corcoran Kostelanetz.

1950: Boris Kostelanetz serves as Special Counsel to the Congressional “Kefauver Committee” in Washington, D.C. The Kefauver Committee made history by allowing its investigation of organized crime in the U.S. to be televised.

1965: Howard F. Corcoran leaves the firm to become a U.S. District Judge in Washington, D.C.

1985: Boris Kostelanetz is dubbed “Dean of Tax Fraud Defense Lawyers” by the New York Times.

1987: Partner Peter L. Zimroth (1943-2021) becomes the City of New York’s Corporation Counsel, the head of the City’s Law Department.

1987: Partner Bryan C. Skarlatos joins the firm. Skarlatos has been named “Lawyer of the Year” for Litigation and Controversy – Tax in New York City by Best Lawyers® for the years 2014, 2017, and 2025.

1990: Kevin Flynn joins the firm, after serving as a Special Trial Attorney for the Office of Chief Counsel of the Internal Revenue Service.

1993: Partner Jules Ritholz passes away. The “Jules Ritholz Memorial Merit Award” was later established by the American Bar Association in his memory, given his role as founder of the ABA Tax Section’s Committee on Civil and Criminal Tax Penalties.

2004:  Megan L. Brackney joins Kostelanetz, following her six years of service as a prosecutor, first in the Missouri Attorney General's Office, and then in the Southern District of New York.

2006: Boris Kostelanetz passes away. The “Boris Kostelanetz President’s Medal” was later established by the New York County Lawyers Association in his memory.

2006 Sharon L. McCarthy joins the firm after serving as a prosecutor for the United States Attorney’s Office for the Southern District of New York for 12 years, including as Chief of the Violent Crimes Unit and Deputy Chief of the Criminal Division. McCarthy is later named “Lawyer of the Year” for Litigation and Controversy – Tax in New York City in the 2026 edition of Best Lawyers®.

2007: The firm moves into its New York City offices at Seven World Trade Center.

2008: Bryan C. Skarlatos creates the annual New York University Tax Controversy Forum, which brings together representatives from the government and expert private practitioners to discuss issues related to tax compliance and enforcement. The NYU Tax Controversy Forum – 18 years later – still draws a broad range of IRS and DOJ officials, along with experienced private practitioners, to share their perspectives on a variety of topics covering a wide range of criminal and civil tax issues.

2010: The “Dean of Tax Education,” Sidney Kess, joins the firm.

2011: Claude M. Millman joins the firm. Millman is later recognized in City & State NY’s “Law Power 100” for the firm’s work in New York City and State government procurement.

2014: Ian Weinstock joins the firm and expands the firm’s trusts and estates practice. Prior to joining Kostelanetz, Ian worked in the legal departments at Morgan Stanley and UBS.

2015: Partner Sharon L. McCarthy is elected to the American College of Trial Lawyers.

2017: Caroline D. Ciraolo and Jay R. Nanavati co-found the firm’s new Washington, D.C., office and join as partners. Ciraolo, who served as the head of the DOJ’s Tax Division before joining Kostelanetz, was later named “Lawyer of the Year” for Litigation and Controversy – Tax in Washington, D.C., for the years 2022, 2024, 2025, and 2026 by Best Lawyers. Nanavati was also later named 2026 “Lawyer of the Year” for Tax Law in Washington, D.C., by Best Lawyers.

2019: Michael Sardar is named a partner in the firm. His practice is focused on tax controversy and white-collar criminal defense matters. He currently serves as Co-Chair of the Federal Bar Association (FBA) Section on Taxation, New York Chapter, and is ranked by Chambers High Net Worth Guide for Tax: Private Client.

2020: Christopher M. Ferguson is named a partner in the firm. His practice concentrates on white-collar criminal defense as well as civil and criminal tax controversies and other regulatory enforcement matters. Later, International Tax Review/World Tax ranks Chris as “Highly Regarded” for Tax Controversy

2020: John D. (Don) Fort, the former Chief of the Internal Revenue Service's Criminal Investigation (CI) Division, joins the Firm as Director of Investigations.

2021: The firm establishes its Spelman College Pre-Law Internship Program.

2022: The firm is listed as “Law Firm of the Year” for Litigation – Tax in the 2022 edition of Best Law Firms®.

2022: Partner Jay R. Nanavati is elected to the American College of Trial Lawyers.

2023: Chambers USA selects the firm’s pro bono program as one of the nation’s top ten for the year. 

2023: Sidney Kess passes away after 13 years with the firm.

2024: The firm gains an Atlanta, GA, office when it combines forces with WELTY PC. As a result, Todd Welty and Andy Steigleder join as partners focused on expanding the firm’s already robust tax controversy practice.

2025: An actuary by training, experienced tax attorney Melissa Wiley joins Kostelanetz as a partner in the Washington, D.C., office focused on civil tax controversy matters for business and high-net-worth clients. She serves as the ABA Tax Section’s Vice Chair for Membership, Diversity Inclusion and as a member of the section’s Nominating and Appointments to the Tax Court Committees. She is also the chair of the DC Bar Tax Audits Litigation Committee and the Regent for the Federal Circuit for the American College of Tax Counsel.

2025: Partner Megan L. Brackney becomes Chair of the Tax Section of the American Bar Association.

2025: Victor Suthammanont, former Enforcement Counsel to the Chair of the U.S. Securities and Exchange Commission, joins the firm as a partner focused on white collar criminal defense and securities regulation.

2025: Karen Kelly leaves her position as head of the Department of Justice’s Tax Division to join the firm as a partner focused on civil and criminal tax matters.

2025: The firm opens its Hackensack, NJ, office, with the addition of Frank Agostino, a veteran of the tax bar known for bringing seminal cases that establish favorable law for taxpayers.

2026: The firm is selected as “Law Firm of the Year” for Litigation and Controversy – Tax in the 2026 edition of Best Law Firms.