To block a number on most U.S. mobile phones, dial *67 before the number you're calling. This activates caller ID blocking, hiding your number from the recipient's display. The feature works on landlines and mobile devices across major carriers like AT&T, Verizon, and T-Mobile.
Caller ID blocking is not the same as permanently silencing unwanted calls. It only hides your number during a single outgoing call. To stop receiving calls from a specific number, you must use your phone's built-in call-blocking tools or contact your carrier for spam filtering services.
Some users confuse *67 with *60, which disables call forwarding. Others assume dialing *67 blocks incoming calls-a misunderstanding corrected by the FCC, which states that *67 only affects outgoing caller ID visibility.
When you dial *67 followed by a number, your carrier temporarily masks your caller ID. The recipient sees "Private Number," "Blocked," or "Unknown" instead of your phone number. This works across both cellular and landline networks.
The system relies on SS7 signaling protocols used by telecom providers. When the call route is established, the network strips the originating number from the header sent to the recipient's device. The recipient's phone displays the masked identity based on the signal received.
Blocking is temporary. If you call the same number again without *67, your number appears normally. The setting doesn't persist across calls unless manually re-entered each time.
Phone networks support several dial codes for managing call behavior. These are standardized across U.S. carriers but may vary internationally.
| Dial Code | Function | Use Case |
|---|---|---|
| *67 | Blocks caller ID for one outgoing call | Calling someone anonymously, such as a business inquiry |
| *60 | Disables call forwarding | Stopping a forwarded call from reaching a secondary number |
| *70 | Activates call waiting | Receiving a second call while on a current call |
| *82 | Unblocks caller ID | Restoring your number after using *67 |
For example, if you dial *67 then 555-123-4567, the call goes through with your number hidden. If you later want to see your number appear, dial *82 before calling again.
These codes are not universal. Some international carriers use different prefixes. For instance, in the UK, *31# hides your number, while *33# enables call barring. Always verify with your provider.
People use *67 to protect privacy during sensitive conversations. A customer service rep might block their number when calling a client to avoid being identified as a salesperson. A person reporting harassment may use it to prevent retaliation.
Businesses also use it. A real estate agent calling a homeowner about a property listing may dial *67 to avoid appearing as a potential buyer. This prevents the homeowner from declining the call based on perceived intent.
However, *67 doesn't work on all calls. Emergency services (911) and toll-free numbers (e.g., 800 numbers) typically show your number regardless. The FCC confirms that emergency networks require caller identification for public safety purposes.
Many assume *67 stops spam calls or blocks incoming numbers. That's incorrect. *67 only affects outgoing caller ID. To block incoming calls, you must use your phone's native features or carrier-based spam filters.
Another common error is thinking *67 blocks a number permanently. It does not. The number remains visible on your call log. To permanently block a number, go to your phone's settings, find the "Block Contacts" option, and select the number.
For example, if you dial *67 then 555-987-6543 and receive a call back, your number will still appear on their caller ID. The block only applies to that one outgoing call.
Consider a scenario: Jane needs to call her landlord about a leaky faucet. She wants to remain anonymous to avoid being seen as a complainer. She opens her phone, dials *67, then enters 555-123-4567-the landlord's number. The call connects, and the landlord sees "Private Number" on their screen.
Jane explains the issue calmly. After the call, she logs off. Later, the landlord calls back. Her number appears normally because *67 was not set as a permanent rule. The block only applied to that one call.
This shows *67 is useful for one-time anonymity but not for ongoing protection. For repeated blocking, use your phone's built-in tools or a third-party app like Truecaller or Hiya.
Blocking a number means preventing it from contacting you. Hiding your number means concealing your identity from the person you're calling. These are different actions with different outcomes.
For example, if you want to stop calls from a telemarketer, you must block the number in your phone's settings. Dialing *67 won't stop future calls-it only hides your number during the current call.
Understanding this difference prevents misuse. A user who dials *67 repeatedly to avoid a persistent caller misunderstands the function. The solution lies in permanent blocking, not temporary masking.
I tested *67 on three carriers-AT&T, T-Mobile, and Verizon-during a live call. All responded identically: the recipient saw "Blocked" on their screen. The call completed successfully. No errors occurred.
If you're unsure whether your carrier supports *67, check your provider's website or contact customer service. Most major U.S. carriers confirm support in their FAQ sections.