Caller ID is a feature that displays your phone number on the recipient's device when you make a call. For landlines, it is provided through NTT's Number Display service, while for mobile phones, it is a standard feature. Being able to check the caller's number before deciding whether to answer makes it a fundamental tool for nuisance call prevention.
Number notification is controlled using special codes. Dialing 184 before the phone number withholds your number, while 186 sends it. As a line-wide setting, you can choose between always-notify (default) and always-withhold, with the special codes overriding that setting for a single call. For example, to notify your number for a specific call from a line set to always-withhold, use 186.
A common misconception is that "notifying your number also shows your name to the recipient" - only the phone number is transmitted. Names appear only when the number is registered in the recipient's contacts or in a nuisance call database. With a phone number lookup app installed, business names and user reviews may display even for numbers not in contacts.
In business, displaying the company's main number is standard practice. By showing the company number rather than individual direct lines, return calls can be received at the main number. However, note that caller ID spoofing technology means displayed numbers are not always accurate. The spread of the STIR/SHAKEN protocol is expected to eventually enable automatic number legitimacy verification. Review caller ID usage in how to handle unknown calls.