E.123 is an international standard by the standardization union (ITU-T). It provides guidelines for the presentation of telephone numbers, email addresses, and web addresses in print, on letterheads, and similar purposes.
As described by the ITU, in E.123: "+" is the "International Prefix Symbol" used in a "Telephone number, E.123 international notation". For example:
| Telephone number, national notation (full number dialling) |
(0607) 123 4567 |
| Telephone number, E.123 international notation |
+22 607 123 4567 |
