IRS Expands List of Substances Subject to Superfund Excise Taxes

The IRS recently added 21 new chemicals to the List of taxable substances subject to the Superfund Chemical Excise Taxes and corrected a typographical error in guidance on the spelling of sodium nitrilotriacetate monohydrate and prescribed a tax rate of $3.97 per ton for the substance, effective July 1, 2022.

The Superfund Chemical Excise Taxes apply to manufacturers, producers or importers who sell or use “taxable chemicals” or “taxable substances” that are manufactured or produced in the U.S. or are imported into the United States. The tax is applicable if the chemicals or substances are considered taxable under §4661 or §4672 of the Internal Revenue Code (“Code”). Businesses must analyze the chemical composition of all of their products and determine where along the supply chain any taxable chemicals or substances are imported into, or produced the U.S., and by whom.

The following substances were added to the List according to the Notice published in the Federal Register on August 4, 2025:

Polyphenylene sulfide

Cellulose acetate (degree of substitution = 1.5–2.0)

4,4′- isopropylidenediphenol-epichlorohydrin copolymer

Nylon 6

Caprolactam

Methyl ethyl ketoxime

Iso-butanol

Diethylene glycol

Monomethyl ether

Ethylene glycol  phenyl ether

Methoxytriglycol

Propylene glycol methyl ether acetate

Propylene glycol methyl ether

Propylene glycol n-propyl ether

Propylene glycol phenyl ether

Di-isobutyl carbinol

Di-isobutyl ketone

Methyl isobutyl carbinol

Cyanuric acid

Potassium bicarbonate

Potassium carbonate

Sodium chlorite.

The effective date for purposes of the excise tax under §4671 of the Code for the taxable substances added to the list is January 1, 2026.

The updated List and prescribed tax rates for taxable substances will be included in the instructions to IRS Form 6627, Environmental Taxes.

In November 2021, President Biden signed into law the Infrastructure Investment and Jobs Act, which revived and expanded long dormant excise taxes (known as the Superfund Chemicals Taxes) used to address hazardous waste sites in the United States. The new taxes, which went into effect on July 1, 2022, apply to the sale of certain chemical substances, and to an importer’s sale or use of specified substances.

For more information, contact Liskow attorneys Caroline Lafourcade, Greg Johnson, or Clare Bienvenu.