Mailsort

Mailsort is a five-digit address-coding scheme used internally by the Royal Mail (the UK's postal service) for the automatic direction of mail. The first three digits, the Residue Selection Code, identify an area corresponding to one or more postcode districts. The last two digits, called the Direct Selection code, identify a postcode group within the district.

Mail users who can present mail sorted by Mailsort code (not necessarily down to the fifth digit) and in quantities of 4000 upwards receive a discounted postal rate.

Although the majority of people in the UK use the Postcode, the mailsort code is now used for automated sorting. The postcode failed in its objective, partly because its inflexibility led to numerous initial two-letter codes being directed to a single main sorting office, and this led to some addresses having non-obvious characters. Furthermore, errors were introduced by the easy confusion by autotype reading of some characters of often hand-written addresses.

First three digits of mailsort code (the residue)

Residue	Location
160-171	Scotland
210-212	Northern Ireland
220-227	North West England
270-290	North Wales, North West & Isle of Man
340-349	Yorkshire
361-368	North East England
420-426	East Midlands & Birmingham
440-444	West Midlands, Mid-Wales, East Anglia
540-550	North Midlands
560-561	Channel Islands
630-641	Outer London
701-718	London
719-724	Northern Home Counties
726-738	South East England
940-948	South West & South Wales
960-967	South & West England