The geographical location is reported using a five digit numerical code. The first digit is the single-digit code to indicate State or Territory. The remaining four digits are the numerical code for the Statistical Local Area (SLA) within the State or Territory.

The single digit codes for the states and territories and the four digit codes for the SLAs are as defined in the Australian Standard Geographical Classification (ASGC).

The ASGC is updated on an annual basis with a date of effect of 1 July each year. The codes for SLA are unique within each State and Territory, but not within the whole country. Thus, to define a unique location, the code of the State or Territory is required in addition to the code for the SLA.

The Australian Bureau of Statistics '(ABS) National Localities Index (NLI) (ABS Catalogue number 1252.0) can be used to assign each locality or address in Australia to a SLA. The NLI is a comprehensive list of localities in Australia with their full code (including State or Territory and SLA) from the main structure of the ASGC.

For the majority of localities, the locality name (suburb or town, for example) is sufficient to assign a SLA. However, some localities have the same name. For most of these, limited additional information such as the postcode or State can be used with the locality name to assign the SLA. In addition, other localities cross one or more SLA boundaries and are referred to as split localities. For these, the more detailed information of the number and street of the person's residence is used with the Streets Sub-index of the NLI to assign the SLA.

If the information available on the person's address indicates that it is in a split locality but is insufficient to assign an SLA, the code for the SLA which includes most of the split locality should be reported. This is in accordance with the NLI assignment of SLA when a split locality is identified and further detail about the address is not available.

The NLI does not assign a SLA code if the information about the address is insufficient to identify a locality, or is not an Australian locality. In these cases, the appropriate codes for undefined SLA within Australia (State or Territory unstated), undefined SLA within a stated State or Territory, no fixed place of abode (within Australia or within a stated State or Territory) or overseas should be used.

Geographical location is reported using Statistical Local Area (SLA) to enable accurate aggregation of information to larger areas within the Australian Standard Geographical Classification (ASGC) (such as Statistical Subdivisions and Statistical Divisions) as well as detailed analysis at the SLA level. The use of SLA also allows analysis relating the data to information complied by the Australian Bureau of Statistics on the demographic and other characteristics of the population of each SLA. Analyses facilitates by the inclusion of SLA information include:

• comparison of the use of services by persons residing in different geographical areas,
• characterisation of catchment areas and populations for establishments for planning purposes, and
• documentation of the provision of services to residents of States or Territories other than the State or Territory of the provider.