Number portability is the ability of a customer to retain their existing phone number(s) when changing their carriage service provider (CSP). This allows consumers to choose between competing CSPs based on price, quality, type of service and (for mobile phone users) coverage without the inconvenience and expense of having to take a new number when moving between providers.
Number portability also eliminates the need for callers to contact directory services to find someone's new number or for people to miss calls as callers continue to dial the old number.
Industry provision of number portability is managed under the 
Telecommunications Act 1997 and the Telecommunications Numbering Plan 1997 (the Numbering Plan).
Number portability applies to the following services:
- local services-predominantly supplied using numbers in the (02), (03), (07) and (08) number ranges (but excludes telex or paging services)
- freephone services-numbers which start with the digits 18 and local rate services-numbers which start with the digits 13
- mobile services-numbers which start with the digits 04 (excluding analogue mobile phone service numbers)
Geographic Number Portability
Local number portability (LNP) was introduced for geographic numbers in 1997. While in general, LNP allows customers to change their telephone provider and keep their telephone number, it does not guarantee consumers can keep their telephone number if they move to a different geographic location. Local numbers in Australia contain specific geographic information. Further information on LNP is available from the Australian Communications and Media Authority (ACMA).
Freephone and Local Rate Number Portability
Freephone and Local Rate number (FLRN) portability allows porting for customers with telephone numbers beginning with the digits 13x or 180x. FLRNs are managed differently from other numbers for the purposes of allocation and porting. The Numbering Plan delegates responsibility for allocating FLRNs to an industry body called Industry Number Management Services (INMS), an independent not-for-profit organisation that administers a centralised reference database of FLRNs released by the ACMA for allocation to CSPs, and for porting between CSPs. Please visit ACMA Number Portability for further information.
Mobile Number Portability
Mobile number portability (MNP) covers all digital mobile service numbers irrespective of the technology used (GSM or CDMA networks) except for satellite-only mobile services.
Australian Goverment
