The EC Number is the unique numerical identifier assigned to chemical substances on European Union regulatory inventories. The umbrella term covers three sub-inventories: EINECS (the European Inventory of Existing Commercial chemical Substances, listing substances on the EU market between 1971 and 1981), ELINCS (the European List of Notified Chemical Substances, listing substances notified to EU regulators after 1981), and the NLP list (No-Longer-Polymers, substances reclassified from polymers to non-polymers under historical EU rules). The format is a seven-digit number split as three-three-one with hyphens (e.g. 215-185-5 for sodium hydroxide; 200-289-5 for benzene). For chemicals on the EU market, the EC number is the primary regulatory identifier, alongside the CAS number, which is the global identifier.
EC format and structure
The EC number has three parts separated by hyphens:
- First three digits identify the substance’s position in the inventory
- Next three digits continue the position numbering
- Final single digit is a check digit
The check-digit calculation differs from CAS but works similarly, typos in EC numbers can be caught by the check-digit failure. Online ECHA tools at echa.europa.eu/information-on-chemicals validate EC numbers automatically.
The EC number range encodes the source inventory:
| Range | Source inventory | Significance |
|---|---|---|
| 200-000-0 to 310-000-0 (approximately) | EINECS | Substances on the EU market between 1971 and 1981 |
| 400-000-0 to 499-999-9 (approximately) | ELINCS | Substances notified after 1981 under the Dangerous Substances Directive |
| 500-000-0 to 599-999-9 | NLP | Polymer-reclassified substances |
| 600-000-0 onwards | List numbers (post-2008) | Substances that received a “list number” (functionally an EC equivalent) when registering under REACH but lacking a true EC entry |
The “list number” mechanism (600+ range) is sometimes mistakenly called an EC number. Strictly, list numbers are issued by ECHA for substances registered under REACH without a pre-existing EC entry. Functionally they act as EC numbers for regulatory reference.
CAS and EC: when they differ
For most substances the relationship is 1:1, one CAS number, one EC number. Several edge cases break this:
| Edge case | Effect |
|---|---|
| Substance listed on EINECS but no CAS number assigned | EC exists, no CAS |
| Substance assigned a CAS but never listed on EU inventory | CAS exists, no EC |
| Two CAS numbers for related substances mapped to one EC entry | Many CAS, one EC |
| One CAS substance listed on multiple EU sub-inventories under different EC numbers | One CAS, many EC |
For routine commodity chemicals the relationship is clean. For specialty chemistries, polymer products, and reaction products, the mapping can be ambiguous. ECHA’s substance information portal at echa.europa.eu/substance-information provides authoritative resolution.
Use in REACH and CLP
The EC number is the primary identifier on:
- REACH registration dossiers, every registered substance is identified by its EC number plus CAS where available
- CLP classification entries, harmonised classifications in CLP Annex VI use EC numbers as the substance reference
- SVHC Candidate List entries, every SVHC substance has an EC number listed
- REACH Authorisation List (Annex XIV) entries, same
- Restriction List (Annex XVII) entries, same
For an EU importer running REACH compliance on Chinese-origin chemicals, the EC number is the key into ECHA’s databases. The Chinese factory’s SDS may use only the CAS reference; the EU importer cross-walks to the EC number for ECHA queries.
How to look up an EC number from a CAS number
Three reliable routes:
- ECHA Substance Information portal at echa.europa.eu/information-on-chemicals, free; search by CAS, IUPAC name, EC number, or substance name; returns the authoritative EC entry.
- The CAS Common Chemistry portal at commonchemistry.cas.org, free; basic substance pages list the EC number when available.
- PubChem at pubchem.ncbi.nlm.nih.gov, free; broad cross-reference database; lists EC numbers and many other identifiers.
For routine industrial chemicals all three sources agree. For specialty or borderline cases, ECHA is the authoritative source for EU regulatory matters.
What an EC number does not tell you
Common misconception: an EC number means the substance is REACH-registered. It does not. The EC number simply means the substance is on an EU inventory. Whether the substance has been REACH-registered, and at what tonnage band, is a separate query. Many EC-listed substances have no current REACH registration (e.g. substances listed on EINECS but never marketed in the EU above the 1 t/yr threshold post-2008).
For an EU importer, the EC number is the gateway to the regulatory question, not the answer. The full REACH-registration check at the registered-volume band is needed before importing.
Operator note: the list-number gap
Chinese factories supplying substances to the EU market under REACH registration sometimes have only a list number (600-range) rather than a true EC number. The list number behaves like an EC for regulatory reference but is not on EINECS, ELINCS, or NLP. EU customers occasionally reject documentation referencing only a list number, expecting an EC number. The fix: cite both the CAS and the list number explicitly, with a note that the substance was registered under REACH without prior EC inventory listing.
Related terms
CAS Number is the global substance identifier; EC is the EU-specific equivalent. REACH registrations use EC as a primary key. CLP classifications use EC as a primary key. IUPAC name is the systematic chemical name that complements CAS and EC.