The short answer: dial *67 on most landlines and cell phones

When you dial *67 before entering a phone number, your number does not appear on the recipient's caller ID. Instead, they see "Unknown," "Blocked," or "Private Number." This works on most carriers in the United States, whether you use a landline, mobile phone, or VoIP service like Magicjack or Vonage.

The feature is called per-call blocking because you set up it for each individual call. You do not need to set it up in advance or contact your phone company. Just dial *67, wait for a tone or dial tone, then enter the number you want to call.

Some carriers and phone systems use different codes. AT&T, Verizon, T-Mobile, and most regional carriers use *67. A small number of systems use *141 or other codes, but *67 is the standard across most of North America.

Key Takeaways

  • Dialing *67 before a phone number hides your caller ID on that single call only.
  • The recipient sees "Unknown" or "Blocked" instead of your phone number.
  • *67 works on most cell phones, landlines, and VoIP services without advance setup.
  • Some recipients can still see your number if they have call trace or special blocking features, or if you call a business with advanced phone systems.
  • Blocking your number does not prevent the call from being recorded or traced by law enforcement if they have a warrant.

When *67 works and when it does not

Per-call blocking works reliably for calls to most personal phone numbers. The person you call sees a blocked or unknown number, and your actual number stays hidden from their phone and their bill.

It does not work when you call toll-free numbers, 911, or directory information. Those services are designed to receive your number regardless of blocking. If you call a business with a modern phone system — a bank, hospital, or large company — the system may capture your number even though the person answering sees it as blocked. Some businesses use call trace features that can reveal a blocked number to their security team.

If the person you call has paid for a service that reveals blocked numbers, they may see your actual number. These services are uncommon but do exist. Your carrier may also have settings that override *67 in certain situations, though this is rare on consumer plans.

How to set up permanent number blocking instead

If you want your number blocked on every call you make, not just one at a time, you can request permanent blocking from your phone company. This is sometimes called "anonymous call rejection" or "caller ID blocking." Contact your carrier — Verizon, AT&T, T-Mobile, or your local provider — and ask them to enable it on your account.

Permanent blocking usually costs nothing on cell phone plans, though some carriers charge a small monthly fee for landlines. Once it is turned on, every call you make shows as blocked unless you dial *82 before the number to unblock that specific call. This is the reverse of *67: instead of blocking one call, you unblock one call when your default is to block all of them.

The downside is that many people do not answer calls from unknown numbers. If you use permanent blocking, the person you call may let it go to voicemail or decline the call. For this reason, most people use *67 only when they need it rather than blocking all calls.

Why someone might want to block their number

People block their numbers for many reasons. You might not want a business to have your personal number when you call for information. You might be calling someone you do not know well and prefer not to share your number until you know them better. You might be returning a call to someone who called you, and you want to keep your number private.

Blocking your number is legal in the United States. You have the right to make a call without revealing your identity, with the exceptions noted above (911, toll-free numbers, and some business systems).

It is not legal to use number blocking to harass, threaten, or defraud someone. If you call repeatedly with a blocked number to intimidate or deceive someone, that is a crime. Law enforcement can trace a blocked call if they have a warrant, even if the recipient cannot see your number.

The difference between blocking your number and blocking calls from others

Blocking your own number (what *67 does) is different from blocking calls from someone else. When you block a caller, you prevent their calls from reaching you. When you block your own number, you prevent your number from showing up on their phone.

To block incoming calls on most phones, go to your phone's settings, find "Call Blocking" or "Blocked Numbers," and add the number you want to block. On iPhone, open the Phone app, find the number in your recent calls or contacts, tap the info button, and select "Block this Caller." On Android, open the Phone app, long-press the number, and tap "Block Number." The blocked caller can still call you, but the call goes straight to voicemail and you get no notification.

Your phone company may also offer a call-blocking service. Verizon Call Filter, AT&T Call Protect, and T-Mobile Scam Shield are carrier-level tools that block spam and robocalls before they reach your phone. These are separate from the blocking you do on your phone itself.

What happens if you block your number and the call does not go through

If you dial *67 and the call fails to connect, it is usually because the recipient's phone system rejected the blocked call. Some businesses, government offices, and private individuals set their phones to reject all calls from blocked numbers. In that case, your call will not ring through, and you will hear a message like "The person you are calling does not accept calls from unknown numbers."

If this happens, you have two options. You can dial *82 before the number to unblock your caller ID for that call, which will let it go through. Or you can call from a different phone, call back later, or send a text message instead. Text messages do not show your caller ID the same way voice calls do, though the recipient will still see your number in their contacts or message thread if you are already in their phone.

Frequently Asked Questions

Can someone trace a blocked call?

Law enforcement can trace a blocked call with a warrant, and some advanced phone systems used by businesses can capture your number even though you blocked it. The person you call cannot trace it themselves, but they can report the call to police if it was threatening or harassing, and police can then obtain your number through legal channels.

Does *67 work on all cell phone carriers?

*67 works on AT&T, Verizon, T-Mobile, and most regional carriers in the United States. A very small number of carriers or phone systems use different codes like *141. If *67 does not work on your phone, contact your carrier to ask what code they use for per-call blocking.

Will the person I call see that I blocked my number?

Yes, they will see "Unknown," "Blocked," "Private Number," or "Restricted" on their caller ID instead of your name or number. They will know a call came in from a blocked number, but they will not know who you are unless you tell them.

Can I block my number when texting?

Text messages do not use the same caller ID system as voice calls, so *67 does not work for SMS. The recipient will see your phone number in the message. If you want to text without revealing your number, you would need to use an app like Google Voice or a temporary phone number service, though those have their own privacy trade-offs.

What if I want to block my number on all calls, not just one?

Contact your phone company and ask them to enable permanent caller ID blocking on your account. Once it is on, your number will be blocked on every call unless you dial *82 to unblock a specific call. Be aware that many people do not answer calls from blocked numbers, so this may reduce the chance someone picks up when you call.