*#31#, #31# and *31# on iPhone: What They Do and How to Turn Them Off

The number 31 confuses people because the same three characters do opposite things depending on where the stars and hashes go. One version hides your number, one shows it, and one tells you which setting you have. Here is each one, plus how to fix the most common complaint: "my iPhone calls show as No Caller ID and I did not ask for that".

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What does 31 mean in a phone code?

In the GSM standard, service 31 is CLIR, Calling Line Identification Restriction. In plain English: whether the person you call can see your number. It is your network that applies it, so these codes work the same on any GSM phone.

Code	What it does	How long
#31# + number	Hides your number	That call only
*31# + number	Shows your number	That call only
*#31#	Checks your line's default setting	Changes nothing

A simple way to remember it: the hash hides, the star shows, and star-hash checks.

How do I use #31# on iPhone?

Open Phone > Keypad and type #31# immediately followed by the full number, for example #31#07700900123, then press Call. The person you call sees "No Caller ID", "Private number" or "Unknown". It applies only to that call.

You can also save a contact with #31# in front of the number, so that person never sees your number. That is useful, but it is also the most common reason people later find calls showing as private and cannot work out why.

Does #31# still work?

Yes, on most GSM networks in the UK, Europe, Asia, the Middle East and Africa. It does not work everywhere: some carriers block it, some override it for certain numbers, and in the US the carriers use *67 instead. The quickest test is to call another phone you own, or a friend, with #31# in front and see what they see.

What does *#31# show?

Dial *#31# on its own and press Call. Your network replies with your default outgoing caller ID setting. If it says caller ID restriction is off or not active, your number is shown by default. If it says restriction is on, your number is hidden on every call unless you dial *31# first. The exact wording depends on the carrier.

How do I turn off #31# so my number shows again?

If your calls show as No Caller ID and you want your number visible, work through these in order:

1. Check Settings. Go to Settings > Apps > Phone > Show My Caller ID (Settings > Phone on older iOS) and turn it on.
2. Check the contact. Open the contact you called and look for #31# at the start of the number. Delete it.
3. Check the line. Dial *#31#. If restriction is on and the Settings switch is missing or greyed out, the carrier has set it on your account. Ask them to remove it.
4. For one call, dial *31# before the number to show it just that time.

Is *#31# the same as *#30#?

No. *#30# checks CLIP, whether you can see the numbers of people who call you. *#31# checks CLIR, whether they can see yours. If incoming calls on your iPhone all appear as Unknown, *#30# is the code to try.

When will a hidden number still be seen?

Emergency services always receive your number. Some toll-free and business lines can still see it, and many people set their phones to reject private calls. iMessage and SMS always show your number or Apple Account. More detail, including *67 and *82 for the US, is in how to hide your caller ID on iPhone.

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