- A petition by Zeon Chemicals L.P. requests addition of styrene isoprene block copolymer (x+z=482, y=2,178.51, a=1.70) to the taxable substances list.
- The substance is a triblock copolymer elastomer used primarily in adhesive formulations.
- Taxable chemicals constitute 25.94 percent by weight; petitioner calculated a tax rate of $2.56 per ton.
- Written comments and hearing requests are due by November 30, 2026.
Petition Filing and Current Status
The Internal Revenue Service issued a notice on October 1, 2026, announcing receipt of a petition to add styrene isoprene block copolymer, known as SIS Rubber, to the list of taxable substances under section 4672(a) of the Internal Revenue Code.
The chemical has the formula (C8H8)x-(C5H8)y-(C8H8)z-(C33H56N4OS2)a with x+z equal to 482, y equal to 2,178.51, and a equal to 1.70. It is sold in pellet form and used mainly in adhesive formulations.
This notice makes the petition public and invites comments. Publication does not constitute a determination that the list will be modified.
Petitioner and Substance Details
Zeon Chemicals L.P., an importer and exporter of the material, submitted the petition. The filing date for determination purposes is February 8, 2026.
Proposed classification numbers are HTSUS 4002.99.0000, Schedule B 4002.99.0000, and CAS 25038-32-8. The predominant production method identified is block polymerization of isoprene and styrene in cyclohexane using a catalyst.
According to the petition, taxable chemicals make up 25.94 percent of the materials by weight. The petitioner calculated a tax rate of $2.56 per ton based on conversion factors for benzene, ethylene, propylene, butylene, nitric acid, methane, ammonia, chlorine, and sodium hydroxide.
Comment Period and Submission Process
Written comments and requests for a public hearing must be received on or before November 30, 2026. Electronic submission is preferred through the Federal eRulemaking Portal at regulations.gov using docket number IRS-2026-1032.
Comments may alternatively be mailed to the IRS at the address provided in the notice. All comments become part of the public record and are posted without change.
If a hearing is scheduled, its time and place will be announced in a future Federal Register notice.
Existing Tax Debt Questions
This notice addresses only the potential addition of a specific chemical substance to the Superfund excise tax list and does not concern income tax, tax debt collection, or eligibility for relief programs. Individuals or businesses with separate questions about IRS or state tax liabilities may consider professional evaluation of their situation.
Republic Tax Relief offers private tax-resolution services for individuals and businesses with IRS or state tax issues and advertises a free, no-obligation initial consultation. Readers can contact the firm to ask about suitability, scope, fees, and availability of help communicating with the IRS.
Announcement covered: Oct 1, 2026.
General information only, not individual tax, legal, or financial advice. Rules, deadlines, and eligibility depend on your circumstances. Check current official guidance or consult a qualified professional.
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