# European Community number

The European Community number (EC number) is a unique seven-digit identifier that was assigned to substances for regulatory purposes within the European Union by the European Commission. The EC Inventory comprises three individual inventories, EINECS, ELINCS and the NLP list.

## Structure

The EC number may be written in a general form as: NNN-NNN-R, where the N represents digits and R is a check digit. The check digit is calculated using the ISBN method. According to this method, the check digit R is the following sum modulo 11:
    $R=(N_{1}+2N_{2}+3N_{3}+4N_{4}+5N_{5}+6N_{6}){\bmod {1}}1$
If the remainder R is equal to 10, that combination of digits is not used for an EC number. To illustrate, the EC number of dexamethasone is 200-003-9. N$_1$ is 2, N$_2$ through N$_5$ are 0, and N$_6$ is 3.
    ${\frac {2+2\!\times \!0+3\!\times \!0+4\!\times \!0+5\!\times \!0+6\!\times \!3}{11}}={\frac {20}{11}}=1+{\frac {9}{11}}$
The remainder is 9, which is the check digit.
There is a set of 181 ELINCS numbers (EC numbers starting with 4) for which the checksum by the above algorithm is 10 and the number has not been skipped but issued with a checksum of 1.

## EC Inventory

The EC Inventory includes the substances in the following inventories. The content of these inventories is fixed and official.
| Inventory | Scope | Format | Number of entries (if fixed number of entries) |
| European Inventory of Existing Commercial Chemical Substances (EINECS) | Substances, excluding polymers, that were recorded as being commercially available in the EU from 1 January 1971 to 18 September 1981. These were considered registered under Article 8(1) of the Dangerous Substances Directive (67/548/EEC). They are considered phase-in substances under the REACH Regulation. | 2xx-xxx-x 3xx-xxx-x | 100,102 |
| European List of Notified Chemical Substances (ELINCS) | Substances notified under the Dangerous Substances Directive Notification of New Substances (NONS) that became commercially available after 18 September 1981. | 4xx-xxx-x | 4,381 |
| No Longer Polymers (NLP) | The definition of polymers was changed in April, 1992 with the result that substances previously considered to be polymers were no longer regarded as polymers. Consequently, a list, called the NLP-list (No Longer Polymer), was made of such substances that were not covered by the polymer definition but were placed on the market between after 18 September 1981 and 31 October 1993. | 5xx-xxx-x | 703 |

## List numbers

European Chemicals Agency (ECHA) also applies the EC number format to what it calls "List number". The number are assigned under the REACH Regulation without being legally recognised. Hence, they are not official because they have not been published in the Official Journal of the European Union. List numbers are administrative tools only and shall not be used for any official purposes.
| Scope | Format |
| Automatically assigned, e.g. to pre-registrations of substances with a CAS No. | 6xx-xxx-x |
| Assigned to substances after inquiries by the ECHA Substance ID Team | 7xx-xxx-x |
| Automatically assigned to substances identified only with a CAS No. (continuation of the 6xx-xxx-x series) | 8xx-xxx-x |
| Automatically assigned, e.g. to pre-registrations without a CAS No. or other numerical identifier (including reaction masses of more than one substance) | 9xx-xxx-x |