McDermott files amicus brief for National Taxpayers Union Foundation in Tax Court COVID-19 interest case

On September 1, 2026, global law firm McDermott Will & Schulte filed an amicus curiae brief on behalf of the National Taxpayers Union Foundation (NTUF) in Wepplo v. Commissioner, a pending US Tax Court case testing whether the IRS correctly calculated underpayment interest that accrued during the COVID-19 disaster period. The brief responds to the Tax Court’s July 2, 2026 order inviting amicus participation.

At issue is the scope of Internal Revenue Code Section 7508A(d), which generally requires the IRS to disregard a federally declared disaster period when calculating interest, penalties, and additions to tax. The petitioners argue Section 7508A(d) required the IRS to disregard interest accruing from January 20, 2020 through July 10, 2023, even though their underlying tax liabilities predate the pandemic. The Commissioner disagrees, citing a 2021 Treasury regulation that caps the relief period at one year.

McDermott’s brief argues the Tax Court should independently determine the statute’s best reading under Loper Bright Enterprises v. Raimondo, rather than defer to an agency’s regulatory interpretation. The brief contends Congress prescribed a mandatory, self-executing relief period in subsection (d) distinct from the discretionary relief Congress separately authorized Treasury to grant under subsection (a) and that Treasury’s general rulemaking authority or discretionary authority under subsection (a) cannot be used to narrow relief Congress itself provided by statute. The brief further argues that Treasury’s one-year cap exceeds its delegated authority and is invalid under Loper Bright and the Tax Court’s decision in Abdo v. Commissioner.

NTUF is a non-partisan research and educational organization whose Taxpayer Defense Center litigates and files amicus briefs challenging administrative overreach by tax authorities.

The McDermott team representing NTUF includes Brent Bartlett, Ed Froelich, Samuel Hamer, Charles Moll, Shawn O’Brien, and Susan Ryba.