The CO postcode area, also known as the Colchester postcode area,[2] is a group of sixteen postcode districts in the east of England, within nine post towns.
These cover northeast Essex (including Colchester, Clacton-on-Sea, Frinton-on-Sea, Halstead, Harwich, Manningtree and Walton-on-the-Naze) and a small part of south Suffolk (including Bures and Sudbury).
The main sorting office is in Colchester.
The approximate coverage of the postcode districts: