What are the Superfund chemical excise taxes?

Two related federal excise taxes reinstated as of July 1, 2022: a tax under section 4661 on the sale or use of listed taxable chemicals, and a tax under section 4671 on imported taxable substances made from those chemicals. They are reported on Form 720 with Form 6627 attached, and run through 2031.

Does the Superfund tax apply to importers of finished chemical products?

Often yes. The section 4671 tax reaches imported substances made from taxable chemicals — and the IRS continues to expand the list of taxable substances, with new additions effective in 2026. Many importers don't realize a product downstream of listed chemicals can be taxable.

How often are Superfund excise deposits due?

Semimonthly, like other federal excise deposits — a schedule that surprises companies new to excise. The IRS has issued deposit penalty relief covering portions of 2026, which signals both that compliance is hard and that relief is temporary.

Superfund Chemical Excise Tax: What Importers Keep Getting Wrong (2026)

Excise Advisors · Updated July 5, 2026 · Superfund · Importers & manufacturers

Short answer: The reinstated Superfund chemical excise taxes (IRC §§4661 and 4671) run through 2031, deposits are due semimonthly, reporting rides on Form 720 + Form 6627 — and the IRS keeps adding substances to the taxable list, including additions effective in 2026. If you import chemical substances and have never modeled this tax, that's not evidence you're exempt. It's evidence nobody has looked.

Two taxes, one trap

§4661 — taxable chemicals: an excise on the sale or use of listed chemicals by manufacturers, producers, and importers.
§4671 — taxable substances: the companion tax on imported substances derived from those chemicals — the one importers miss, because the product on the invoice doesn't look like a "chemical."

The taxable-substances list is not static. The IRS has continued expanding it — see the 2026 determinations adding new substances — which means a product that was fine last year can be taxable this year.

Why compliance keeps failing

Procurement doesn't talk to tax. The people who know what's being imported (customs brokers, supply chain) aren't the people filing returns.
Rate complexity. Rates vary by chemical and by the chemical composition of imported substances; importers who can't substantiate composition can face default rates that are often worse.
The semimonthly clock. As with all federal excise, deposits run on 15-day periods. The IRS's own Superfund guidance and repeated deposit penalty relief tell you how often companies get this wrong.
Refunds left on the table. Exemptions and credits exist (exports and certain uses among them) — companies overpay almost as often as they underpay.

A 30-minute self-test

Pull your import data for one quarter. If you can't answer these three questions in 30 minutes, commission a review: (1) Which imported products contain or derive from listed chemicals? (2) What did we deposit, per semimonthly period, against those imports? (3) Where are the composition records that support our rate positions?

Import chemicals or chemical-derived products?
Get a free 20-minute exposure scan from a former IRS auditor →

This article provides general information about federal excise tax topics and is not legal, tax, or accounting advice. Rules cited as of July 2026; verify current guidance at irs.gov. ExciseAdvisors · 10 South Riverside Plaza, Chicago, IL 60606.