How to Block Your Number When Making a Call

Blocking your number before making a call — so the recipient sees "No Caller ID," "Private Number," or "Unknown" instead of your digits — is a built-in feature on virtually every modern phone. It works at the network level, meaning your carrier suppresses the outgoing Caller ID signal before it ever reaches the other end. Here's how it works, what controls it, and where things can get complicated.

What Actually Happens When You Block Your Number

When you dial someone, your phone transmits a CLI (Calling Line Identification) signal alongside the call. The recipient's phone or carrier reads that signal and displays your number. Blocking your number sends a suppression flag — technically a CLIR (Calling Line Identification Restriction) request — that tells the network to withhold that data before delivery.

This is different from using a burner app or VoIP service that generates a fake number. CLIR simply hides your number; it doesn't replace it with something else.

One important caveat: emergency services (911 in the US, 999 in the UK, 112 in the EU) can always see your number, regardless of blocking. Certain law enforcement requests can also retrieve it. Blocking your number provides everyday privacy — not anonymity in any absolute sense.

Method 1: The Per-Call Prefix Code 📞

The fastest way to block your number on a single call is to dial a prefix before the number:

This applies only to that one call. Your number shows normally on every other call you make. It works on both landlines and mobile phones, and you don't need a smartphone or any app to use it.

Method 2: Blocking Your Number Permanently Through Phone Settings

If you want every outgoing call to go out with your number hidden, both Android and iOS let you set this as a default — though the exact path depends on your OS version and carrier.

On iPhone (iOS)

Go to Settings → Phone → Show My Caller ID and toggle it off. When greyed out or unavailable, your carrier has locked this setting and you'll need to contact them directly to enable permanent blocking.

On Android

The path varies by manufacturer, but the general route is: Phone app → Settings (three-dot menu or gear icon) → Calls → Additional Settings → Caller ID → Hide Number

On Samsung devices, this is often under Phone → More Options → Settings → Supplementary Services → Show My Caller ID.

Some Android builds label it differently — look for "Caller ID," "Show My Number," or "Outgoing Call Settings." If the option is missing, it may be carrier-restricted.

Method 3: Contacting Your Carrier

Many carriers offer account-level line blocking, where your number is suppressed on all outgoing calls by default. This is managed at the network level, not the device level, which means it persists even if you change phones or SIM cards.

Carriers that offer this typically call it something like "Outgoing Call Restrictions" or "Caller ID Blocking." The availability and any associated fees vary by carrier and plan type — prepaid plans sometimes don't support it.

If your in-phone settings are grayed out, the carrier has almost certainly locked that control. A call to customer service is the only path forward in that case.

Why Blocking Doesn't Always Work 🔍

There are real-world limits to how effective number blocking is:

• Call-screening apps like Hiya, Nomorobo, or Google's spam detection can flag "No Caller ID" calls and send them to voicemail automatically. Many people set their phones to reject unknown callers entirely.
• Business phone systems and PBX setups often reject calls with no Caller ID before they even ring.
• Some carriers un-suppress CLIR on international calls, meaning the recipient may see your number anyway if you're calling across borders.
• VoIP platforms (Zoom Phone, Google Voice, Teams) have their own Caller ID logic that doesn't always respect device-level CLIR settings.

The Variables That Affect Your Experience

The method that works cleanly for one person may run into walls for another. What determines your actual outcome:

• Your carrier and plan type — some restrict Caller ID settings entirely
• Your device OS and version — menu paths and available toggles change with updates
• Who you're calling — landlines, mobile numbers, VoIP numbers, and business systems respond to CLIR differently
• Whether you're calling domestically or internationally — international call handling is inconsistent
• Whether the recipient uses call-screening tools — hidden numbers are often blocked outright

Per-call blocking with a prefix code is the most universally available option, since it requires no settings access and works on almost any phone connected to a standard voice network. Permanent blocking through settings or your carrier is more convenient but depends on factors outside your direct control.

Whether per-call blocking is enough for your needs, or whether you need something more persistent — or even a separate number entirely — depends entirely on how often you need this, who you're calling, and what your carrier actually supports on your specific line.