IRS Seeks Comment on Adding Modified SAN Latex to Superfund Tax List

The Internal Revenue Service issued a notice of filing announcing a petition to add butadiene-acrylonitrile-methyl methacrylate-styrene copolymer, also known as Modified SAN Latex, to the list of taxable substances under section 4672(a) of the Internal Revenue Code. The public docket is IRS-2026-1026 and written comments, or requests for a public hearing, must be received on or before November 9, 2026.

The petition, filed by Zeon Chemicals L.P., identifies the substance by the formula ((C4H6)w(C3H3N)x(C8H8)y(C5H8O2)z) with w=124.79, x=424.05, y=129.62, z=72.41. Classification numbers include HTSUS 4002.11.000, Schedule B 4002.11.000, and CAS numbers 9010-94-0 and 7732-18-5. The petitioner describes the material as a water-based latex used as a binder in lithium-ion battery manufacture.

According to the petition, taxable chemicals constitute 72.98 percent by weight of the material. The petitioner proposes a tax rate of $10.33 per ton, applying conversion factors of 0.13 for butadiene, 0.42 for propylene, 0.17 for ammonia, 0.32 for benzene, 0.07 for ethylene, 0.03 for methane, and 0.14 for sulfuric acid. Production is characterized as emulsion polymerization of the listed monomers.

Petition filing dates are listed as November 18, 2025 for determination purposes and April 1, 2025 for purposes of Rev. Proc. 2022-26 as modified by Rev. Proc. 2023-20. The notice clarifies that publication of the petition does not constitute a Treasury or IRS determination of accuracy. Comments may be submitted electronically via the Federal eRulemaking Portal at regulations.gov, referencing the docket number, or mailed to the IRS address provided. For further information, Jacob W. Peeples can be reached at (202) 317-6855.

The IRS will post all received comments without change to regulations.gov, and any public hearing will be announced in a subsequent Federal Register notice.