Calling number display (CND) allows you to see the telephone number of incoming calls displayed on the screen of your telephone or on a CND unit attached to your telephone.
A CND service can help you decide whether or not to answer a call. Some handsets and units also record the details of calls you may have missed.
How does CND work?
CND works in two parts:
The telephone service used to make the call must be set up to allow the number to be displayed (CND-enabled).
The person receiving the call must have a display handset or CND unit to see your number if your telephone service is CND-enabled. If your telephone service is not CND-enabled, the other party will not be able to see your number even if they have a display handset or CND unit.
What type of numbers can be displayed as CND?
Public numbers can be displayed as CND, including:
geographic numbers (numbers beginning with 02, 03, 07 or 08)
freephone numbers (1800 numbers)
local rate numbers (13 and 1300 numbers)
How do I know if my number is being displayed?
To check whether your number is displayed when you make calls, dial 127 220 from your fixed telephone line or *#31# from your mobile phone.
How can I prevent my telephone number from being displayed?
You can take steps to ensure your number is not displayed for all calls or for individual calls only. This is known as CND blocking.
To arrange for CND blocking on all calls from your telephone (known as permanent CND blocking), contact your telephone service provider.
To block CND for an individual call, all you have to do is dial the blocking code—1831—and then the number you are calling. Generally, this will ensure that the person you are calling will not see your number.
What if I have an unlisted number?
If you have a telephone service with an unlisted number, CND will be automatically permanently blocked. You can contact your telephone service provider to remove the permanent CND block.
If you are calling from a telephone service with an unlisted number or one that has permanent CND blocking and you would like to display your number for an individual call, all you need to do is dial the unblocking code—1832—and then the number you are calling.
Sometimes even if you block CND your number is displayed
When someone calls the emergency service number 000, the number — including unlisted or CND-blocked numbers — will be displayed. This allows the emergency service operator to contact the most appropriate emergency service.
Law enforcement agencies are legally permitted to gather information from telephone service providers and ISPs—even if you have an unlisted number or have blocked CND.
Some internet service providers (ISPs) have agreements with telephone service providers that mean they are given the telephone numbers their customers use to access their ISP accounts. This includes unlisted numbers and the numbers of services with CND blocking.
Even if you don't use an ISP there may be instances when an ISP is given your telephone number by a telephone service provider. This can happen if you allow someone to access their ISP from your telephone service.
What should I do if I block or enable CND and it isn't operating properly?
Contact your telephone service provider. If the problem is not resolved, you can raise the matter with the Telecommunications Industry Ombudsman (TIO), who may investigate and help resolve your complaint
Calling number display guideline
An industry guideline for CND has been developed so that telephone service providers, ISPs and others offering and using CND products follow a common set of processes. Further information is available in the Communications Alliance fact sheet: Calling Number Display.
Please note: this document is intended as a guide only and should not be relied on as legal advice or regarded as a substitute for legal advice in individual cases.