What is calling number display?
Calling number display, or CND, is a feature that allows you to see the telephone number of incoming calls displayed on the screen of your telephone or displayed on the screen of a CND unit attached to your telephone. Having a CND service can help you decide whether or not to answer a call and some handsets and units also record the details of calls you may have missed.
How does CND work?
CND works in two parts. Firstly, the telephone service used to make the call must be set up to allow the number to be displayed (CND-enabled). Secondly, the person who is receiving the call must have a telephone handset with a display screen or CND unit attached to their telephone and they must arrange with their telephone service provider to receive a CND service.
This means that even if your telephone service is CND-enabled, if the person you are calling does not have a display handset or CND unit and they do not receive a CND service from their provider, they will not be able to see your number.
Conversely, if your telephone service is not CND-enabled, then no matter if the person you are calling has a display handset or CND unit and is receiving a CND service, they will not be able to see your number.
How do I know if my number is being displayed?
Your telephone may be CND-enabled. This depends on whether your telephone service has an unlisted number or how your telephone service provider initially set up your service. It means that any person you call who has a display handset or CND unit and is receiving a CND service can see your number when you call them.
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?
In most circumstances, it is your choice whether or not the number of the telephone service you are calling from is displayed to the person you are calling. You can take steps to ensure your number is not displayed for all calls you make 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. Permanent CND blocking will be provided to you at no cost. However, there may be some charge if you change this permanent arrangement within six months of the original request.
If you do not want a permanent CND block, it is quite easy to block CND on a call-by-call basis. 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 and generally your number will not be displayed to the person you call. You can change this arrangement if you wish. Contact your telephone service provider to remove the permanent CND block.
Permanent CND enabling will be organised for you at no charge, however if you change this arrangement within six months there may be a fee. Changing your telephone service to CND-enabled does not change your telephone service's status as an unlisted number.
If you are calling from a telephone service with an unlisted number or one which 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 of the telephone service used, even if the service has an unlisted number or is CND-blocked, will be displayed to the emergency service operator. This allows the operator to contact the most appropriate emergency service.
In addition, some Internet service providers (ISPs) have agreements with telephone service providers which 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.
ISPs are only permitted to use these numbers to detect fraud, assist in billing and call management, and for credit control. ISPs are not allowed to use these numbers for telemarketing, data collection or any other purpose. Your ISP will tell you if they receive client calling numbers from telephone service providers and how they use these numbers.
In some circumstances, law enforcement agencies are legally permitted to gather information about you and how you use your service from telephone service providers and ISPs. These powers are available to law enforcement agencies even if you have an unlisted number or have blocked CND.
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.
For example, if you have a house guest who has a laptop and needs Internet access, you might allow your guest to use your telephone line to connect to the Internet. If your guest's ISP has an agreement with the telephone service provider that has carried the connection, the ISP may be given your telephone number. This can happen even if you have an unlisted number or have CND blocked.
What should I do if I block or enable CND and it isn't operating properly?
If you become aware that your CND blocking or enabling isn't working properly, talk to 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. You can contact the TIO on freephone 1800 062 058.
Calling number display code
An industry code for CND has been developed to ensure telephone service providers, ISPs and others offering and using CND products abide by a common set of rules.
The ACMA has fact sheets on a range of topics.
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.