These cover west and central Berkshire (including Reading, Bracknell, Crowthorne, Hungerford, Newbury, Thatcham and Wokingham) and north Hampshire (including Basingstoke, Hook, Tadley and Whitchurch), plus a small part of south-east Oxfordshire (including Henley-on-Thames) and very small parts of Buckinghamshire and Wiltshire.

The original RG3 district for west Reading was recoded to RG30 and RG31 in January 1995, due to the rise in population in that area.

[3] In the same year, the original RG11 district for Wokingham and Crowthorne was recoded to RG40, RG41 and RG45, while the northern part of the RG12 district for Bracknell was recoded to RG42.

Hungerford and Thatcham was also separated from the Newbury-dependent RG15 and RG16 postcodes, subsequently being recoded into RG17 and RG18-19, respectively, thus reducing the extent of the Newbury postal town to RG14 and RG20.

RG26-29 ceased to be dependent on the Basingstoke postal town as the areas the postcodes represent were assigned new postal towns.