Every substance on the TSCA Inventory carries a commercial activity designation: active or inactive. The designation is not a historical footnote. It decides whether you can manufacture or import the substance next month without filing anything first, and roughly half the Inventory sits on the wrong side of that line.
As of EPA's July 2026 release, 42,698 substances are designated active and 44,043 are designated inactive. An inactive substance is still on the Inventory. It is still an existing chemical. It is not a new chemical and it does not need a premanufacture notice. What it needs is a Notice of Activity Form B before anyone manufactures or processes it again.
What the two designations actually mean
The rule is 40 CFR part 710, subpart B, written to carry out TSCA sections 8(b)(4) and 8(b)(5). It defines the terms narrowly, and the definitions matter more than the plain-English reading of the words.
An active substance is any of four things: an interim active substance, a naturally occurring substance under 710.27(b), a substance added to the Inventory through a Notice of Commencement received on or after June 21, 2006, or a substance EPA designated active after receiving a notice under the subpart.
An inactive substance is one that EPA designated inactive because no notice arrived, effective 90 days after EPA identifies it for that designation.
The term doing the quiet work is interim active substance, which the rule defines as any substance reported under the Chemical Data Reporting rule at 40 CFR part 711 as manufactured in any of the calendar years 2010 through 2015. Those substances were designated active without anyone filing for them. Everything else that predates June 21, 2006 had to be claimed.
That is why the split is close to even. The designations were not a judgment about safety or usefulness. They recorded who answered during a reporting window that closed years ago.
Why an ordinary chemical ends up inactive
Interim active status came free to any substance already caught by Chemical Data Reporting, which only reaches manufacturers above its own volume thresholds. A substance made in modest quantity, or made only as a site-limited intermediate, or imported by a company that read the 2017 notice as somebody else's problem, could pass through the window unclaimed.
So inactive does not mean obsolete, superseded, or suspect. It means unreported. Plenty of inactive substances are perfectly ordinary articles of commerce that nobody happened to speak up for, and a supplier quoting you one today may not know its designation any better than you do.
The window that closed, and the one that did not
There are two forms, and confusing them is the most common mistake.
Notice of Activity Form A was the retrospective one. Manufacturers had from August 11, 2017 to February 7, 2018. Processors had until October 5, 2018. Both windows are shut. Form A is finished business and no longer available to you.
Notice of Activity Form B is the forward-looking one under TSCA section 8(b)(5), and it is the form that still matters. Section 710.30(b)(1) says it must be submitted before a person manufactures or processes the inactive substance, but not more than 90 days prior to the anticipated date of manufacturing or processing.
Read that sentence twice, because a good deal of published guidance gets it backward. The 90 days is a ceiling on how early you may file, not a waiting period you must serve. There is no review clock in the rule comparable to the 90-day PMN review. You file before you start, within the 90 days leading up to your anticipated start date, and EPA moves the substance to the active Inventory. Planning for a mandatory three-month wait, and planning to file three months out and then start, are two different project schedules, and only one of them is what the regulation says.
Five activities that do not trigger a notice at all
Section 710.27(a) exempts a short list. None of these require a Form B, whatever the substance's designation:
- Manufacturing or processing in small quantities solely for research and development.
- Importing or processing the substance as part of an article.
- Manufacturing or processing as described in 720.30(g) or (h).
- Manufacturing or processing solely for export, under 720.30(e) or 721.3, unless the Administrator has made a finding under TSCA section 12(a)(2).
- Manufacturing or processing solely for test marketing purposes.
Section 710.27(b) adds naturally occurring substances, with a catch worth knowing: if you manufacture the substance by any means other than those described in 710.4(b), the exemption does not apply, even where the same substance could have been produced naturally.
The research and development exemption is the one that leads people astray. It covers the lab work. It does not cover the first commercial batch, and the transition from one to the other is exactly the moment a Form B becomes due.
The obligation you may not actually have
Section 710.25(c) ends with a clause worth reading closely. A person must file a Form B before manufacturing or processing an inactive substance, "unless the presence of the inactive substance on the confidential portion of the Inventory is not known to or reasonably ascertainable by the person."
That phrase is defined at 710.3: all information in a person's possession or control, plus all information that a reasonable person similarly situated might be expected to possess, control, or know.
The duty is therefore bounded by what you could reasonably find out, which is the legal counterpart to the data problem described below. A substance sitting on the confidential portion of the Inventory appears in no public file under its CAS number, so there are cases where the obligation does not attach because it could not reasonably have been discovered. That is not permission to avoid looking. Reasonably ascertainable covers what your suppliers can tell you when asked, and it covers what a bona fide intent submission to EPA would return.
There is a related trap in 710.25(a). A company was excused from filing Form A if it held a CDX receipt showing someone else had filed for the same substance. The rule says plainly that the receipt is no basis for exemption from 710.25(c) if the substance was ultimately designated inactive because that other person withdrew their Form A. Relying on another company's filing left you exposed to their change of mind.
When more than one company touches the same volume
Section 710.33(b) covers co-manufacturers, importers and processors. If two or more persons intend to handle a particular volume of an inactive substance, they may decide among themselves which one submits the notice. If no notice is submitted, every one of them remains subject to the requirement and EPA will hold each liable.
An agreement about who files moves the work, not the obligation. Toll manufacturing and import arrangements are exactly where this goes wrong, because each party can reasonably assume the other is closer to the paperwork.
How the filing actually happens
Notices go through EPA's Central Data Exchange. You register in CDX, then prepare the notice in the Chemical Information Submission System using its e-NOA module. Section 710.39 requires a separate notice for each chemical substance, so a portfolio of inactive substances is a stack of individual filings rather than one list.
Section 710.35 requires records documenting anything reported to EPA, kept for five years beginning on the day the notice was submitted. The Form B itself is a short submission compared with a premanufacture notice, which is the practical reason the active or inactive distinction is worth checking early: discovering an inactive designation a week before a production run is an annoyance, and mistaking one for a new chemical is a PMN you did not owe.
How to check a substance
EPA publishes the non-confidential portion of the Inventory as a CSV about every six months, with the activity status in each record. You can also search it through EPA's Substance Registry Services.
Ambrose holds the July 2026 release, 70,774 substances, of which 36,522 are active and 34,252 are inactive, and every lookup in our regulatory compliance platform reports which EPA release the answer came from. A regulatory answer without a date on it has no shelf life, and this one expires roughly every six months.
One limit applies to us, to EPA's CSV, and to every commercial service built on it. EPA maintains a confidential portion of the Inventory that it does not publish, identified only by accession number and generic name. A substance absent from the public portion is not thereby unlisted. It may be on the confidential Inventory, and establishing that takes a bona fide intent to manufacture submitted to EPA, not a database search. Any tool that reports a miss as "not on the TSCA Inventory" is overstating what it knows, and acting on that overstatement means filing a premanufacture notice you may not owe.