Tax Notes quoted Kostelanetz counsel Usman Mohammad in an article titled “IRS Used Repealed Guidance in Whistleblower Case, Court Says” about his work representing the estate of Joseph Insinga, alongside partners Caroline Rule and Bryan C. Skarlatos.
On August 8, 2025, in the case Estate of Insinga v. Commissioner, the D.C. Circuit reversed and remanded a Tax Court’s decision that affirmed the IRS Whistleblower Office’s denial of an award to Insinga. The D.C. Circuit agreed with Kostelantz’s arguments that the Whistleblower Office a) applied an incorrect, overly restrictive, legal standard when it denied Mr. Insinga an award, and b) relied on an administrative record that was arbitrarily incomplete. The Tax Court then affirmed by itself applying the correct standard to an incomplete record instead of remanding to the Whistleblower Office.
“The decision demonstrates that the courts will carefully review whistleblower award decisions and require the IRS to apply the whistleblower rules correctly, which can only increase confidence in the program and lead to potentially higher recoveries” by the IRS, Usman told Tax Notes.
Insinga was a Dutch bank executive who first blew the whistle on two U.S. corporations in 2007, submitting numerous documents to the IRS showing that the corporations engaged in improper tax avoidance schemes with the Dutch Bank.
Although it recovered millions of dollars from the U.S. corporations, the Whistleblower Office denied Insinga an award in April 2013 because the government was already investigating the two corporations, applying 2012 proposed IRS regulations’ incorrectly stringent standard for whistleblower awards that was later disavowed in 2014 final regulations. Insinga immediately filed a Tax Court petition, but he died before the court ruled on the petition a decade later, in December 2023.
You can learn more about IRS whistleblower regulations and the Insinga estate’s successful appeal by reading the complete article here.
About Usman
Usman’s tax controversy practice includes defending clients in federal and state criminal matters involving issues such as tax shelters, payroll tax, check cashing, structuring cash deposits, filing false returns, and failing to file tax returns. He also has extensive experience with government procurement award protests, Article 78 proceedings involving procurement matters, foreign asset reporting issues, IRS responsible person and trust fund recovery penalty matters, IRS whistleblower matters, and IRS collection cases.
About Caroline
Caroline’s practice focuses on civil and criminal tax matters and complex civil litigation. She also advises accounting firms about best practices when outsourcing work offshore, including compliance with confidentiality requirements of the Internal Revenue Code, the Gramm-Leach-Bliley Act, and the FTC Safeguards Rule.
About Bryan
For more than thirty-five years, Bryan has represented corporations and individuals in sensitive matters, many of which involve negotiation or litigation with government agencies. He is internationally recognized for his work on tax controversies, audits, appeals, and litigation, criminal tax investigations, and white-collar criminal prosecutions. Bryan also has an active practice providing tax and estate planning advice.
