Do You Need CAS Numbers for Your FDA Listing?

You've got a supplier certificate of analysis with a CAS number on it, and you're staring at your MoCRA product listing wondering if that number needs to go somewhere. Short answer: probably not where you'd expect, and here's why the confusion happens so often.

INCI names are the primary language of a listing

Cosmetic ingredient lists, whether on a label or in a regulatory filing, are built around INCI names. That's the international naming system where water is Aqua, glycerin is Glycerin, and a supplier's fancy trade name for a preservative blend gets broken down into its actual chemical components. MoCRA's product listing requirement centers on this same convention: you're identifying ingredients the way the rest of the industry and the FDA already talk about them.

CAS numbers are a different kind of identifier. They're assigned by Chemical Abstracts Service to pin down a specific substance regardless of what anyone calls it in a formula sheet. One INCI name can sometimes map to more than one CAS number, and some botanical extracts don't have a CAS number at all because they're not single defined chemical entities. That mismatch is exactly why you can't always use one system as a stand-in for the other.

Where CAS numbers actually help

Even when a listing doesn't require a CAS number as a mandatory field, having one on hand is useful for:

• Cross-referencing safety data. If you're pulling toxicology or allergen information to support your safety substantiation, CAS numbers help you find the right entry when a supplier uses regional or older naming conventions.
• Disambiguating a component. If two suppliers describe the same raw material slightly differently, the CAS number is often the fastest way to confirm you're dealing with the same substance before you decide it's a duplicate or a different ingredient entirely.
• Working through a blend. Supplier blends list a trade name on the drum but expand into several INCI components inside. CAS numbers on the underlying safety data sheet help you verify each component is what you think it is, especially before you multiply the blend's percentage in your formula by each component's share of the blend to get its real concentration.

Where CAS numbers do not substitute for INCI

Don't fall into the trap of listing a CAS number instead of an INCI name because it feels more precise. Reviewers, retailers, and cross-border filings are built around INCI naming conventions. If your only identifier for an ingredient is a CAS number and you can't map it back to an INCI name, you have a gap in your documentation, not a shortcut.

This matters more than it sounds like it should, because the same logic shows up whether you're filing in the US, dealing with a retailer's vendor packet, or eventually notifying in a market like Canada, where ingredients are listed by INCI name with a concentration or range. The naming convention travels. CAS numbers are a supporting reference, not a replacement identifier.

A quick way to think about the split

Identifier	Where it's used	What it tells you
INCI name	Labels, ingredient lists, regulatory filings	The standardized name used across markets and regulators
CAS number	SDS section 3, safety literature, internal QA	The precise chemical identity, useful for cross-checking
Trade name	Supplier invoices and spec sheets	Marketing name only, never appears on a filing

What this means for MoCRA specifically

MoCRA requires facility registration and product listing with the FDA, along with a named responsible person and safety substantiation. Some small businesses are exempt from registration and listing, so it's worth confirming your status before assuming the full requirement applies to you. But regardless of exemption status, if you're building an ingredient list for any purpose, whether it's the listing itself or the safety file behind it, start with INCI names as your backbone and keep CAS numbers as the supporting detail you reach for when something needs to be double-checked.

If you're mapping a formula from scratch, expanding blends and cross-checking components against both INCI and CAS references is one of the more tedious parts of getting a filing ready. That's a chunk of what Cosmetic Comply automates: it takes your ingredient list, maps everything to INCI names and CAS numbers, expands supplier blends into their real components, and carries the math through before anything gets filed. Useful whether you're getting your first listing together or just trying to confirm an old formula sheet still lines up with what's actually in the bottle.