July 2025: New numbering system for List Numbers
In the coming months, the format of List numbers will be updated. As the current numerical formats are exhausted, the new format will become alphanumeric
27 Mar 2025What are List Numbers?
As many of you know, each substance registered or notified under the REACH or CLP Regulation requires a unique identifier in the REACH-IT submission tool. If a substance is not identified using an EC number and has not previously been registered or notified by any company, REACH-IT will automatically assign a specific List number as an identifier for that substance.
EC numbers are derived from various historical legislative lists, as shown below.
Substances with EC numbers are considered phase-in substances for REACH registration purposes.
Format Source
2xx-xxx-x EINECS (European INventory of Existing Commercial chemical Substances) List
3xx-xxx-x EINECS (European INventory of Existing Commercial chemical Substances) List
4xx-xxx-x ELINCS (European LIst of Notified Chemical Substances) List
5xx-xxx-x NLP (No-Longer Polymers) List
List numbers, however, are purely technical identifiers assigned by ECHA and have no legal significance. This means they should not be used, for example, in Safety Data Sheets or similar documents.
Historically, List numbers and EC numbers have shared the same format: six numeric digits and a check digit, e.g.:
Format Source
1xx-xxx-x Assigned by ECHA
6xx-xxx-x Assigned by ECHA
7xx-xxx-x Assigned by ECHA
8xx-xxx-x Assigned by ECHA
9xx-xxx-x Assigned by ECHA
With the new format, List numbers will maintain the same length but will begin with a letter as the first character. Once all letters are used as the first character, the second character will also become a letter, and so on.
| Old Numerical Format | New Alphanumeric Format |
| 100-000-1 | A00-001-5 |
Some details about the List number calculation method
The check digit for the EC or List number is calculated using the ISBN method. For the purposes of calculation, letters in a List number are assigned numeric values, for example:
A = 10,
B = 11
Letters I, L, and O are not used to avoid being mistaken with the numbers 0 and 1.
The code is established based on the following logic:
NNN-NNN-R, where N represents alphanumeric characters and R is a check digit.
R = (N1 + 2*N2 + 3*N3 + 4*N4 + 5*N5 + 6*N6) mod 11
If N is a letter, it represents a numeric value (A = 10, B = 11, etc.)
It is important to note that List numbers assigned before the format change will remain unchanged and will not be affected by this update.
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