Zip codes in the UK are called Postcodes. In the UK postal code system, any property can be uniquely identified by the postcode plus house number or house name. Larger businesses and isolated properties such as farms often have a unique postcode. Postcode structure is alphanumeric with the following seven possible permutations:
A9 9AA
A9A 9AA
A99 9AA
AA9 9AA
AA9A 9AA
AA99 9AA
There are only 5 cities/districts using the A9 9AA format:
B: Birmingham, West Midland
L: Liverpool, Merseyside
M: Manchester
N: North London
S: Sheffield, South Yorkshire
The postcode for the Delivery Office of Royal Mail in Sheffield is S1 1AA