CAS Numbers vs INCI, Which Goes on the Label

A new maker asked me recently whether she needed to print CAS numbers next to each ingredient on her lotion label, since she'd seen them on her supplier's safety data sheet and figured more information was safer. It's a reasonable instinct, and it's also backwards from how these two identifiers are actually meant to be used.

Two systems, two jobs

INCI, the International Nomenclature of Cosmetic Ingredients, exists specifically for labeling. It's the standardized naming system that lets a consumer in Canada, France, and Australia all recognize "Aqua" as water regardless of what the product is called or where it's sold. INCI names are what belong on your package, listed in the format your market requires, in Canada that means a bilingual English and French ingredient declaration.

CAS numbers, issued by the Chemical Abstracts Service, exist to uniquely identify a substance for scientific, regulatory, and record-keeping purposes. They're precise in a way that's useful for matching data across documents, a safety data sheet, a technical data sheet, a regulatory filing, but they're not designed for a consumer standing in a store trying to figure out if a product contains something they're allergic to. Nobody's expected to recognize 106-24-1 on sight the way they might recognize "Geraniol."

Where each one actually shows up

Document or context	Which identifier is used
Product label / package	INCI name
Cosmetic Notification Form (CNF)	INCI name, with CAS number as supporting reference in your records
Safety data sheet, Section 3	Both, typically CAS number alongside a chemical or common name
Your internal formulation records	Both, ideally, for cross-referencing
Supplier technical data sheet	Both, though INCI names are what you carry forward to your own documentation

The CNF itself is built around INCI names and concentrations, that's the format Health Canada's Cosmetic Notification System expects. The CAS number's real job happens earlier in your process, when you're trying to confirm that the "Rosemary Extract" one supplier sells you is chemically comparable to what another supplier calls something slightly different, or when you're cross-checking a substance against the Hotlist and want certainty that you're looking at the right entry rather than a similarly-named but distinct substance.

Why trade names never appear on either

This is worth stating plainly because it trips people up constantly: a supplier's trade name, the catchy blend name on the drum label, never appears on your CNF and never appears on your product label. It gets mapped, always, to INCI names for the label and the filing, with CAS numbers as your internal cross-reference for confirming you've mapped it correctly. If your formula sheet still has "Blend X47" sitting where an ingredient list should be, that's an unfinished step, not a shortcut.

A practical example

Say your SDS lists a preservative component as follows:

• Chemical name: Phenoxyethanol
• CAS number: 122-99-6
• INCI name: Phenoxyethanol (in this case they happen to match in wording)

Compare that to a botanical ingredient:

• Supplier trade name: "GreenLeaf Complex"
• INCI name: Camellia Sinensis Leaf Extract
• CAS number: often none, or not meaningfully assigned, since it's a variable natural extract rather than a single defined chemical substance

Your label carries "Camellia Sinensis Leaf Extract." Your CNF carries the same INCI name with a concentration. Your internal records keep the CAS number where one exists, purely so you or anyone auditing your files later can trace the substance back to source documentation with certainty.

The takeaway for your filing workflow

Keep both identifiers in your master ingredient records, but don't confuse their audiences. INCI is written for the person buying the product. CAS is written for the person, or the system, verifying what the substance actually is behind the scenes. Mixing them up on a label isn't dangerous, but it's non-compliant, and leaving CAS numbers out of your internal records makes future cross-checking much harder than it needs to be.

Cosmetic Comply handles this mapping automatically, matching each ingredient you provide to both its INCI name and CAS number, so your filing carries the right identifier in the right place without you having to manually cross-reference supplier paperwork every time.