Kent is TN because that postcode area was originally centered on Tonbridge/Tunbridge Wells , while Taunton is TA because the code was assigned from Taunton as its named postal area. The letters are mostly mnemonic area codes chosen by the UK postcode system, not county names, so a county like Kent can contain multiple postcode areas and a town like Taunton can define one of them.

Why they differ

UK postcode areas were designed around postal routing and delivery offices , not administrative counties. That’s why the first letters usually come from a prominent town or area name, and why the same county can span several postcode prefixes.

Kent’s case

Kent is a county, but its postcodes are split across several areas, including TN , CT , ME , and others, because Royal Mail organized them around delivery geography rather than county borders. So TN does not mean “Kent”; it means the Tonbridge/Tunbridge Wells postal area.

Taunton’s case

TA is the postcode area for Taunton and surrounding parts of Somerset, so the code comes directly from the town name. In other words, TA is a town-based postal label, just like many other UK area codes.

Simple rule

  • County name ≠ postcode area.
  • Postcode area = postal geography , usually named after a key town.
  • A county can have many postcode areas, and one postcode area can cover more than one town.

In short, TN and TA reflect how the postcode system was built for mail sorting, not how counties are named.