What Are Anonymous Calls?
An anonymous call is a phone call where the caller intentionally hides their caller ID. In Japan, callers can withhold their number by dialing "184" before the number or by configuring their line settings. Both landlines and mobile phones can make anonymous calls, and the recipient's display will show "Anonymous" or another indication of a withheld number. This applies regardless of whether the call originates from a landline with an area code like 03 or 06, or a mobile number starting with 090 or 080.
When you cannot tell who is calling, it is hard to judge whether to answer or leave it, and only the unease stays with you. This article covers everything from why anonymous calls happen to specific countermeasures, carrier-specific settings, and how to report them to police.
Why You Receive Anonymous Calls
Legitimate Reasons for Withholding Caller ID
Some businesses automatically withhold their number due to PBX (Private Branch Exchange) settings. Hospitals contacting patients or government agencies calling for official purposes may also use anonymous calling. Individuals sometimes choose to withhold their number for privacy. Job-related calls from prospective employers or callbacks from real estate agents are common everyday examples. On NTT landlines without the Number Display service, numbers may not appear at all, which can be confused with anonymous calls.
Malicious Anonymous Calls
Anonymous calls are also used for stalker harassment, prank calls, and as a precursor to fraud - for example, checking whether someone is home. Late-night or early-morning anonymous calls are especially likely to be harassment and can cause significant psychological distress. With schemes that use the phone as their entry point, such as bank transfer fraud or refund scams, treat a short call that states no purpose as a reason for caution in itself. If anonymous calls keep going silent and then disconnecting, add automated dialing by robocalls to the possibilities, and read up on how to handle silent calls as well.
Basic Ways to Handle Anonymous Calls
There are several options depending on your situation. The safest response is simply not to answer, though some people may need to pick up for work-related reasons. Here is a summary of approaches:
- Enable anonymous call blocking: Your smartphone or landline can automatically reject anonymous calls. Because only anonymous calls are turned away, this is the first step to try when you still want to receive calls that show a number.
- Use the Number Request service: This paid option from NTT East and NTT West plays an automated message asking anonymous callers to redial with their number displayed. It requires a subscription, so check the price and the conditions that apply in your provider's official information.
- Let voicemail handle it: Do not answer anonymous calls and let voicemail pick up. Legitimate callers will leave a message.
- If you must answer, never share personal information: Do not reveal your name, address, or date of birth. Ask "Who is calling?" to verify the caller's identity first.
- Record the call: Use a call recording app to preserve evidence of threats or harassment. Recording a call you are a party to is widely used as a way to preserve evidence, but if you are unsure how the recording may be handled, consult the police or a lawyer before you rely on it.
How to Block Anonymous Calls by Device
iPhone (iOS)
On iPhone, go to Settings > Phone > Silence Unknown Callers and turn it on. This silences calls from numbers not in your contacts, including anonymous calls, and sends them directly to voicemail. Note that this also silences calls from any unregistered number.
Android
On Android, open the Phone app settings, go to Blocked Numbers, and enable "Unknown callers." The exact menu names may vary by manufacturer, but the basic steps are the same.
Landline Phones
For NTT landlines, subscribing to the "Number Request" service automatically rejects anonymous calls. The same service is available for Hikari Denwa (fiber-optic phone). Many phone handsets also have built-in anonymous call rejection - check your manual to enable it.
What to Do About Repeated Anonymous Calls
If anonymous calls keep coming, there may be stalking or harassment involved.
- Save your call log: Record the date, time, frequency, and content (if you answered) in detail. Screenshots and call recordings are valuable evidence.
- Contact the police: Visit the Community Safety Division at your nearest police station. For non-emergencies, you can also call the police consultation line at #9110.
- Request protection under the Anti-Stalking Act: Japan's Anti-Stalking Act treats phone harassment as one form of "stalking-type conduct." A warning is issued by a police headquarters chief (the Superintendent General of the Metropolitan Police Department, a prefectural police headquarters chief, or a police station chief), while a prohibition order is issued by the prefectural public safety commission. A prior warning is not a precondition: where there is an urgent need to protect someone's safety, a prohibition order can be issued without a hearing.
- Consider changing your number: If call blocking is not enough, contact your carrier to arrange a number change.
Laws and Rights Regarding Anonymous Calls
Making an anonymous call is not illegal in Japan by itself. However, repeated anonymous calls as harassment may violate the Anti-Stalking Act or local nuisance prevention ordinances. Article 2, paragraph 1, item 5 of the Anti-Stalking Act lists "telephoning and saying nothing, or, despite being refused, repeatedly telephoning, sending documents, transmitting by facsimile, or sending email" as one form of "stalking-type conduct." Repeating such conduct amounts to "stalking," which carries imprisonment for up to one year or a fine of up to one million yen (Article 18); stalking committed in violation of a prohibition order carries imprisonment for up to two years or a fine of up to two million yen (Article 19). The Act also regulates obtaining location information from GPS devices and the like without consent (Article 2, paragraph 3), so it can apply where such conduct overlaps with phone harassment.
Fraud committed via anonymous calls falls under the Penal Code's fraud provisions (Article 246) and can result in imprisonment for up to 10 years. If you are a victim, do not give up - consider pursuing legal remedies.
Common Misconceptions About Anonymous Calls
"All anonymous calls are dangerous"
Not every anonymous call is malicious. As noted above, PBX settings, official business, and personal privacy are all legitimate reasons. Calls from prospective employers, hospital test results, or law firm callbacks are everyday examples. Blocking all anonymous calls indiscriminately may cause you to miss important communications.
"The source of an anonymous call can never be traced"
It is certainly difficult for an ordinary individual to identify the source of an anonymous call. Investigative authorities, however, can query carriers for call records through the procedures set out in law. In stalking and threat cases, room remains for an investigation to reach the caller. Rather than deciding in advance that the caller can never be found, preserve your call log and any recordings, then consult the police.
Protecting Seniors from Anonymous Call Scams
Elderly people are the primary targets of phone fraud, making anonymous call countermeasures especially critical. According to National Police Agency statistics, 65.4% of the victims of organized phone-based fraud in 2024, excluding corporate victims, were aged 65 or older. Family members should set up their elderly relatives' phone environments to prevent victimization.
- Install a phone with automatic recording warnings: A phone that announces "This call is being recorded" is meant to make it harder for a caller who does not want to be named to keep the conversation going. Some municipalities offer a subsidy toward the purchase, so check with your local government office.
- Use nuisance call prevention devices: These devices play a warning message when a call arrives and record the call automatically. Some areas run lending programs through local governments or the police, so ask your local government office. See also how to block nuisance calls.
- Establish a family code word: Agree on a secret phrase to verify identity when someone calls asking for money.
- Use voicemail even when home: Screen calls through voicemail and call back after checking the message. This filters out calls that leave no message and gives you time to confirm who is calling before you call back.
Summary - Protecting Yourself from Anonymous Calls
Dealing with anonymous calls comes down to proactive settings and calm responses. Enable anonymous call blocking, and if you must answer, never share personal information - this is fundamental to phone number privacy. Repeated anonymous calls may constitute a crime, so preserve evidence and consult the police. Do not face this alone; seek help from the appropriate authorities.