Postal boundaries are included in their own layer and contain two separate files: high-resolution boundaries and a global boundary file. The high-resolution file contains the most granular level boundaries available for the following countries:
- Japan
- Portugal
- The Netherlands
- United Kingdom
The global boundary file contains a set of postal boundaries at the most granular level that can be delivered as a boundary for all but the four countries listed above Not all countries have a postal system or source data needed to provide detailed postal boundaries. Boundaries may not represent the full roster of postal codes for a given country. Most often this is attributed to postal codes that are PO boxes or unique delivery points, such as businesses or large residential buildings, which can only be represented as points.
All countries include, at a minimum, a single polygon in the postal layer, showing the country border. This is intended to help support a display use case, ensuring contiguous coverage in a regional map rendering. There is an attribute field indicating the number of digits of the postal code for each record.
Alternate postal names are included for boundaries in Australia and the United States. Postal codes in Australia which have more than one possible name have Multiple Localities - See Index as the name. The multiple names are stored in the AUS_LOCALITY_INDEX.txt file and can be joined by postal code.