Super Output Areas are aggregations of Output Areas. There are 3 types of Super Output Area, Lower Layer, Middle Layer, and Upper Layer.

The first character is either E for England or W for Wales. The next two characters are either 01 for Lower Layer, or 02 for Middle Layer and the remaining six characters make up the unique 6-digit tag for each zone.

There are 32,482 Lower Layer Super Output Areas in England
There are 6,780 Middle Layer Super Output Areas in England
There are likely to be approximately 2,000 Upper Layer Super Output Areas in England.

For more information about Super Output Areas see the National Statistics website.

10an = Super Output Area

Z99999999 = Not known