How to Block Your Number When Dialing: A Complete Guide to Caller ID Privacy

Blocking your number before making a call — so the recipient sees "Unknown," "Private," or "No Caller ID" instead of your digits — is a built-in feature of virtually every phone system. It's straightforward in principle, but the exact method, reliability, and limitations vary depending on your device, carrier, and the network on the other end.

What "Blocking Your Number" Actually Does

When you make a standard phone call, your number is transmitted as part of the Caller ID signal. Blocking your number suppresses that signal before it reaches the recipient's handset — or instructs the network to withhold it.

This is done through a system called CLIR (Calling Line Identification Restriction). It's a network-level feature, not a software trick. Your carrier's infrastructure intercepts the request and strips your number from the outgoing call data.

The result on the recipient's end depends on their device and carrier settings — they may see "No Caller ID," "Private Number," "Unknown," or simply a blank field.

How to Block Your Number: Method by Method

Using a Per-Call Prefix Code

The most universal method works on any phone — smartphone or landline — without changing any settings.

Dial *67 before the number (in the US and Canada):

*67 + [area code] + [phone number] 

Example: *67 555 867 5309

This blocks your number for that call only. Your Caller ID returns to normal on the next call. This prefix is the most reliable option when you only need occasional privacy.

📞 Outside the US, the prefix differs by country. In the UK, use 141. In Australia, use 1831. Always check your country's CLIR prefix before assuming *67 applies.

Blocking Your Number Permanently on iPhone

To hide your number on every outgoing call by default:

1. Go to Settings
2. Tap Phone
3. Select Show My Caller ID
4. Toggle it off

When disabled, all calls will go out with your number withheld unless you manually unblock on a per-call basis using *82 (the US code to temporarily unblock a permanently hidden number).

Blocking Your Number Permanently on Android

The setting location varies by manufacturer and Android version, but the general path is:

1. Open the Phone app
2. Tap the three-dot menu or Settings
3. Select Calls or Call Settings
4. Look for Caller ID, Show My Caller ID, or Additional Settings
5. Choose Hide Number

Samsung devices running One UI may label this differently than stock Android on a Pixel. If you can't locate it, searching "Caller ID" in your device's settings search bar usually surfaces it directly.

Blocking Your Number on a Landline

Most landline providers support *67 for per-call blocking. For permanent blocking, you'll need to contact your carrier directly — some providers offer Complete Blocking as a free account-level setting, while others require a formal request or charge a small fee.

Important Limitations to Understand

Knowing how to block your number is only part of the picture. Several variables affect whether it actually works as expected.

Emergency Services Always See Your Number 🚨

911 (and equivalent services in other countries) are exempt from Caller ID blocking. No matter what suppression method you use, emergency dispatchers will receive your number. This is a legal and safety requirement, not a carrier choice.

Toll-Free Numbers Can Bypass Blocking

Numbers with 1-800, 1-888, 1-877, and similar prefixes often use ANI (Automatic Number Identification) rather than standard Caller ID. ANI is a billing-system signal that operates independently of CLIR, meaning businesses using those lines may still see your number even when blocked.

Some Recipients Won't Accept Blocked Calls

Many individuals and businesses configure their phones to automatically reject calls from private or unknown numbers. If your call doesn't connect and goes directly to voicemail — or doesn't ring at all — number blocking may be the reason.

VoIP and App-Based Calls Behave Differently

Services like WhatsApp, FaceTime, Google Voice, Zoom Phone, and other VoIP platforms handle Caller ID through their own systems, not traditional PSTN (phone network) rules. *67 typically has no effect on these calls. Privacy settings, if available at all, are managed inside the app itself.

The Variables That Change Your Experience

Your carrier matters. Most major carriers support CLIR fully, but some prepaid or MVNOs (Mobile Virtual Network Operators) may have gaps in how they process blocking requests.

The recipient's network matters. A blocked number hitting an older landline system may display differently than one hitting a modern carrier or VoIP service.

Your use case matters. Someone wanting to block their number occasionally for personal reasons has different needs than a professional making high-volume outbound calls, a journalist protecting a source, or a small business managing client communications. The right approach — per-call prefix, system-level toggle, a dedicated second number via Google Voice, or a business calling platform — shifts based on frequency, professionalism, and how consistently the blocking needs to work.

Your device's software version matters. The location and behavior of Caller ID settings has shifted between Android versions and iOS releases. What's true for iOS 16 may be labeled differently in iOS 17+, and Android 13 versus Android 15 menus diverge by both OS version and device manufacturer.

The underlying technology is consistent — CLIR is a well-established standard — but how reliably it serves your specific situation depends on the intersection of your device, your carrier, who you're calling, and how often you need it.