Districts in the CO area
| District | Main place | Local authority | Sectors | Postcodes |
|---|---|---|---|---|
| CO1 | Colchester | Colchester | 3 | 593 |
| CO2 | Colchester | Colchester | 4 | 944 |
| CO3 | Colchester | Colchester | 5 | 864 |
| CO4 | Colchester | Colchester | 6 | 1,193 |
| CO5 | Tiptree | Colchester | 5 | 977 |
| CO6 | Coggeshall | Colchester | 5 | 1,029 |
| CO7 | Wivenhoe | Tendring | 6 | 1,343 |
| CO8 | Bures | Braintree | 1 | 126 |
| CO9 | Halstead | Braintree | 5 | 928 |
| CO10 | Sudbury | Babergh | 8 | 1,682 |
| CO11 | Lawford | Tendring | 3 | 574 |
| CO12 | Harwich | Tendring | 4 | 644 |
| CO13 | Frinton-on-Sea | Tendring | 3 | 441 |
| CO14 | Walton-on-the-Naze | Tendring | 1 | 246 |
| CO15 | Clacton-on-Sea | Tendring | 7 | 1,368 |
| CO16 | Clacton-on-Sea | Tendring | 4 | 819 |
Main places in the CO area
- Colchester
- Clacton-on-Sea
- Sudbury
- Harwich
- Halstead
- Tiptree
- Walton-on-the-Naze
- Wivenhoe
- Brightlingsea
- West Mersea
- Frinton-on-Sea
- Jaywick
- Kirby Cross
- Berechurch
- Lawford
- Long Melford
- Coggeshall
- Sible Hedingham
- Kelvedon
- Manningtree
- Mistley
- West Bergholt
- Earls Colne
- Little Clacton
- East Bergholt
- Glemsford
- Thorpe-le-Soken
- Elmstead Market
- St Osyth
- Brantham