CO postcode area
The CO area holds 16 districts and 13,771 live postcodes; its largest place is Colchester.
| District | Live postcodes | Largest place with its centre there |
|---|---|---|
| CO1 | 593 | Colchester |
| CO2 | 944 | Layer de la Haye |
| CO3 | 864 | — |
| CO4 | 1,193 | Boxted |
| CO5 | 977 | Tiptree |
| CO6 | 1,029 | Coggeshall |
| CO7 | 1,343 | Wivenhoe |
| CO8 | 126 | Bures Saint Mary |
| CO9 | 928 | Halstead |
| CO10 | 1,682 | Sudbury |
| CO11 | 574 | Manningtree |
| CO12 | 644 | Harwich |
| CO13 | 441 | Frinton-on-Sea |
| CO14 | 246 | Walton-on-the-Naze |
| CO15 | 1,368 | Clacton-on-Sea |
| CO16 | 819 | Little Clacton |
Contains OS data © Crown copyright and database right 2026. Contains Royal Mail data © Royal Mail copyright and database right 2026. Source: Office for National Statistics licensed under the Open Government Licence v3.0. Postcode data is the ONS Postcode Directory, August 2026 edition; counts are live postcodes with a usable location. Northern Ireland postcodes carry a separate licence and are not included; Scotland joins when the site's Scottish coverage does.