How Much of Your Formula Do You Have to Disclose? EU Composition Rules, Explained

For a formulator with a proprietary mixture, Section 3 of the safety data sheet is where the tension between regulatory transparency and trade-secret protection comes to a head. Disclose too little and your SDS is non-compliant. Disclose too much and you've handed a competitor your recipe. The EU rules governing this are more demanding — and less forgiving — than their U.S. counterparts, and they catch a lot of authors who are transcribing a U.S. SDS into an EU format and assuming the disclosure logic carries over. It doesn't.

Here's how composition disclosure actually works in the EU, what you're obligated to reveal, and the narrow legal mechanism that lets you protect a substance identity.

The governing text

EU SDS content is set by Annex II of REACH (Regulation 1907/2006), as amended by Commission Regulation (EU) 2020/878. That amended format has been mandatory for every SDS circulating in the EU since January 1, 2023 — so "we updated our template a few years ago" is not a safe assumption if the update predates 2020/878. The disclosure thresholds themselves reference the CLP Regulation (1272/2008).

The first thing to understand is that EU disclosure obligations are broader than GHS as implemented in the US. In the US, an SDS is generally required only for hazardous products. The EU requires disclosure of certain substances that aren't classified as hazardous at all — because they carry an EU workplace exposure limit, or because they're persistent and bioaccumulative. This is the single most common gap when a U.S.-authored SDS is reused for the EU.

What you must disclose, by case

EU Section 3.2 splits on whether the mixture itself is classified as hazardous under CLP.

If the mixture is classified as hazardous, you must list every substance that:

presents a health or environmental hazard under CLP and is present at or above the lowest applicable threshold — the generic cut-off values, the generic concentration limits, or any specific concentration limit, whichever is lowest; or
has an EU workplace exposure limit, at or above that limit's relevant concentration.

If the mixture is not classified as hazardous, you still must list:

substances with a health or environmental hazard, or with an EU workplace exposure limit, at ≥ 1% by weight (non-gaseous mixtures) or ≥ 0.2% by volume (gaseous mixtures); and
substances that are PBT, vPvB, or on the SVHC Candidate List for reasons beyond those hazards, at ≥ 0.1% by weight.

That 0.1% SVHC threshold deserves its own flag.

The SVHC moving target

Any substance on ECHA's Candidate List of Substances of Very High Concern, present at or above 0.1% w/w in your mixture, must be identified — by name, EC number, CAS number, and concentration range. The catch: the Candidate List is not static. As of early 2026 it holds well over 240 substances, and ECHA updates it roughly twice a year, typically in January and June.

The practical consequence is uncomfortable: an SDS that was perfectly compliant 18 months ago can become non-compliant without you touching the formula, simply because one of your components was added to the Candidate List. Composition disclosure in the EU is not a write-once task — it's a maintenance obligation tied to a list that changes underneath you. This is a strong argument for a system that re-checks your components against the current list rather than relying on a one-time classification.

How concentrations may be expressed

You have two options for stating concentration in Section 3:

exact percentages, in descending order by mass or volume, where technically possible; or
ranges.

Ranges are where trade-secret protection lives for most formulators — but a range is not a license to obscure. It has to be a genuine range, applied appropriately, and it cannot be used to mask the true hazard profile of the mixture. (U.S. authors should note a sharper U.S.-specific rule here: OSHA requires the narrowest possible range, prohibits widening a range to hide a value, prohibits ranges that include zero, and disallows the "~" approximate symbol. The EU is less prescriptive about the symbol mechanics but holds the same underlying principle — the range can't defeat the purpose of disclosure.)

Protecting a substance identity: the CLP Article 24 route

If a concentration range isn't enough and you need to protect the identity of a substance, the EU provides exactly one sanctioned mechanism: the alternative chemical name under Article 24 of CLP. It's narrower than most people expect:

It applies only to substances within a mixture — you cannot request it for a pure substance.
It must be applied for, and approved by, ECHA. It is not something you self-declare.
It is only available for substances meeting the specific criteria in Part 1 of Annex I to CLP.
You must demonstrate that disclosing the real identity would genuinely jeopardize your confidential business information, particularly your IP.

If granted, the alternative name replaces the chemical name in the SDS, and you're relieved of the obligation to provide the CAS number, EC number, and other precise identifiers for that substance. That's the payoff: a real, legal way to keep a key ingredient's identity off the document — but only through ECHA, only for qualifying substances, and only with justification.

A few EU specifics that catch authors off guard

UFI codes. Classified mixtures notified to poison centres via the PCN portal must carry the 16-character Unique Formula Identifier in Section 1. No UFI on a notifiable classified mixture means a non-compliant SDS.
Nanoform identification. Section 3 must explicitly identify nano-forms where present — a requirement that applies wherever nanoforms are in the product, not only where nano-specific registration applies. (If you work in advanced materials, this one is easy to miss and directly relevant.)
ATE, SCL, and M-factor. Since the end of 2022, the acute toxicity estimate, any specific concentration limit, and the M-factor must appear in Section 3 where applicable — notably for components with acute or chronic aquatic toxicity Category 1.
Local language. Chemical identities generally must appear in the official language(s) of the member state where the product is placed on the market.

The takeaway

EU composition disclosure is a layered decision: which substances cross which thresholds, under which of two cases, checked against a list that changes twice a year, expressed in concentrations that protect what they legitimately can — with one narrow ECHA-approved escape hatch for substance identity. It rewards precision and punishes "good enough" transcription from another jurisdiction.

GHSLogic applies the EU Section 3 disclosure logic deterministically — evaluating each component against the correct case and thresholds, flagging SVHC and PBT/vPvB triggers, and showing exactly why each substance does or doesn't have to appear. When the rules say a component must be listed, you'll know which rule, and why.

This post is general regulatory information, not legal or compliance advice. Confirm current requirements against REACH Annex II (as amended by Regulation (EU) 2020/878), the CLP Regulation, and current ECHA guidance before making compliance decisions.