When the SDS and TDS Give Different Numbers, Which Wins

You pull up the safety data sheet for a preservative blend, then pull up the technical data sheet for the same product, and the numbers in front of you don't match. One says the active is present at 18 to 22 percent, the other says 20 percent flat, or worse, one lists a completely different figure than the other. This happens more than you'd think, and there's a reasonable way to resolve it.

Why they disagree in the first place

A safety data sheet has 16 standardized sections, and section 3 is where composition information lives. It's written primarily for hazard communication and workplace safety purposes, and its composition data is often expressed as a range rather than a precise figure, partly for proprietary reasons and partly because SDS composition disclosure rules generally don't require the exact percentage, a range is often considered sufficient for hazard communication purposes.

A technical data sheet, by contrast, is a marketing and formulation support document. It's written to help a formulator understand how to use the product, and it sometimes states a more specific "typical" concentration, or describes the product in terms of active ingredient content that isn't phrased the same way the SDS phrases it.

So the mismatch usually isn't an error, it's two documents serving two different purposes, written by potentially different teams within the same supplier, using different conventions for how precise to be and what exactly is being measured.

The rule for filing purposes

When you need one real number for a notification, here's the priority order that generally makes sense:

1. Ask the supplier directly for the exact percentage used in your specific lot or product code. This is always the best move when the stated figure actually matters, because it resolves the ambiguity at the source rather than guessing which document is more authoritative.
2. If you can't get a direct answer, use the more specific and current document. A range on an SDS isn't wrong, it's just less precise. If the TDS gives a specific "typical" percentage and there's no reason to doubt it, and no supplier response is forthcoming, that specific figure is usually more useful for a filing than a wide SDS range, provided you keep in mind it may be described as "typical" rather than guaranteed.
3. If you're using an SDS range, use the top of the range for anything relevant to a concentration limit or restricted-substance threshold. This is the conservative choice: if an ingredient inside that blend is subject to a hotlist limit or an allergen disclosure threshold, and you're not sure whether your actual concentration sits at the low or high end of the supplier's stated range, assuming the higher figure protects you from underreporting.
4. Document which figure you used and why. If a regulator or a customer ever asks about your filing, "the SDS gave a range, the TDS gave a specific figure, I used the TDS figure because it was more precise and I could not get supplier confirmation in time" is a defensible answer. "I picked whichever number was more convenient" is not.

A concrete example

Say you're using a preservative blend where the SDS lists the active component at "10 to 15 percent" and the TDS states it as "typically 12 percent." You're using this blend at 1 percent of your finished formula.

Source	Stated concentration	Real concentration in your product at 1% use level
SDS (range, conservative top)	15%	0.15%
TDS (typical figure)	12%	0.12%
Supplier direct confirmation	Whatever they confirm	Use this if you get it

If that active ingredient sits anywhere near a restricted-substance threshold, the difference between 0.12 percent and 0.15 percent in your finished product could matter. This is exactly the kind of gap worth resolving with a phone call or email to the supplier rather than guessing.

When it genuinely doesn't matter

Not every discrepancy needs a resolution project. If the ingredient in question isn't close to any concentration limit and isn't a fragrance allergen subject to disclosure thresholds, a reasonable estimate from either document is usually fine for your own formulation records. Save the deeper verification effort for ingredients where the actual percentage changes your compliance obligation, not for every routine emulsifier in the formula.

Cosmetic Comply's ingredient matching flags exactly this kind of ambiguity when it shows up in supplier documentation, so you know which ingredients are worth a follow-up email to the supplier before you file, rather than discovering the gap after your notification is already submitted.