Request a Demo
The U.S. Internal Revenue Service (IRS) announced on August 4, 2025, a significant update to its list of taxable substances under the Superfund chemical excise tax.
This revision adds 21 new substances, bringing the total number of taxable substances to 172. The new tax for these substances will become effective on January 1, 2026.
Background of the Superfund Tax
The Superfund chemical excise tax, originally established under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) of 1980, was designed to fund the cleanup of hazardous waste sites across the United States.
This tax, levied on certain chemical substances, was initially abolished in 1995. However, on December 15, 2021, the IRS announced its reinstatement, with enforcement beginning on July 1, 2022, and continuing through December 31, 2031.
There are two separate Superfund chemical excise taxes:
A tax on the sale or use of "taxable chemicals" under section 4661 of the Internal Revenue Code (section 4661 tax);
A tax on the sale or use of imported "taxable substances" under section 4671 (section 4671 tax).
Specifically, section 4661(a) and 4662(c)(1) impose an excise tax on the sale or use of a taxable chemical by the manufacturer, producer, or importer of the taxable chemical. Section 4671(a) imposes an excise tax on the sale or use of a taxable substance by the importer of the taxable substance.
Newly Added Substances
The 21 newly added taxable substances and their tax rates are shown below:
| Taxable substance | CAS Number | Tax rate per ton |
| Polyphenylene sulfide | 25212-74-2, 26125-40-6 | $ 14.50 |
| Cellulose acetate (degree of substitution = 1.5-2.0) | 9035-69-2 | $ 1.65 |
| 4,4′-isopropylidenediphenol-epichlorohydrin copolymer | 25068-38-6 | $ 14.13 |
| Nylon 6 | 25038-54-4 | $ 14.77 |
| Caprolactam | 105-60-2 | $ 14.77 |
| Methyl ethyl ketoxime | 96-29-7 | $ 11.41 |
| Iso-butanol | 78-83-1 | $ 7.07 |
| Diethylene glycol monomethyl ether | 111-77-3 | $ 5.47 |
| Ethylene glycol phenyl ether | 122-99-6 | $ 10.42 |
| Methoxytriglycol | 112-35-6 | $ 5.66 |
| Propylene glycol methyl ether acetate | 108-65-6 | $ 8.85 |
| Propylene glycol methyl ether | 107-98-2 | $ 10.58 |
| Propylene glycol n-propyl ether | 1569-01-3 | $ 10.43 |
| Propylene glycol phenyl ether | 770-35-4 | $ 13.16 |
| Di-isobutyl carbinol | 108-82-7 | $ 8.57 |
| Di-isobutyl ketone | 108-83-8 | $ 8.67 |
| Methyl isobutyl carbinol | 108-11-2 | $ 7.99 |
| Cyanuric acid | 108-80-5 | $ 2.11 |
| Potassium bicarbonate | 298-14-6 | $ 0.25 |
| Potassium carbonate | 584-08-7 | $ 0.36 |
| Sodium chlorite | 7758-19-2 | $ 2.35 |
Compliance Obligations
For taxable chemicals, the manufacturer, producer, or importer of the taxable chemical is responsible for reporting and paying the section 4661 tax to the IRS. For taxable substances, the importer of the taxable substance is responsible for reporting and paying the section 4671 tax to the IRS.
The Superfund chemical excise taxes are reported quarterly on Form 6627, Environmental Taxes, which is attached to Form 720, Quarterly Federal Excise Tax Return.
