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Glossary · Numbering

What is Private number?

  • Also called: private call, no caller id, withheld number

Reviewed by Sujan ThapaliyaLast updated

Definition

A private number is a call placed with caller ID deliberately withheld, so the recipient sees Private, Withheld or No Caller ID. In North America this is usually done per call with a blocking prefix; in the UK and much of Europe the equivalent prefix is 141.
The three STIR/SHAKEN attestation levels, which underpin how private number behaves in practice: A asserts both that the carrier knows the customer and that the customer may use the calling number, B asserts the customer only, and C asserts neither. A shared number pool can reach B at best, which is why number ownership keeps recurring in these definitions.
Attestation is the backdrop to most caller-ID and deliverability terms, private number included.

In practice

How private number actually works

Withholding is a legitimate feature with a bad reputation, because the people who use it most consistently are the ones recipients least want to hear from. Answer rates for withheld calls are a fraction of those for identified calls, which makes it a poor choice for any business that wants a conversation.

It is also self-defeating on outbound sales calls. A withheld number cannot be called back, so every prospect who would have returned the call is lost, and the calls that do connect start from a position of suspicion.

The opposite approach — a registered business name displayed on every call, signed so carriers trust it — is what actually moves answer rates.

Worked example

Answer rates for withheld calls run a fraction of those for identified ones, and none of them can be returned. For a business that is two losses from one setting.

Private number: common questions

How do I make a private call?
Dial the per-call blocking prefix before the number — *67 in North America, 141 in the UK. It withholds your number for that call only. Some carriers also offer permanent withholding on the line.
Why do my calls show as private when I did not set that?
Usually a line-level setting inherited from the account or the handset, or a PBX that is not passing a valid caller ID. On a business system it is almost always a configuration issue rather than a deliberate choice.
Should a business ever withhold its number?
Rarely. It removes the callback path, suppresses answer rates, and cannot be signed at full attestation. The legitimate cases are narrow — safeguarding and some clinical contexts — and even those usually use a switchboard number instead.

Sources

  1. Combating Spoofed Robocalls with Caller ID Authentication — Federal Communications CommissionThe STIR/SHAKEN framework, the attestation levels carriers sign calls with, and the mandate requiring providers to authenticate caller ID.
  2. 47 U.S.C. § 227 — Restrictions on the use of telephone equipment — Cornell Legal Information InstituteThe Telephone Consumer Protection Act itself — the consent requirements, calling-hours limits, and private right of action.
  3. ITU-T Recommendation E.164 — The international public telecommunication numbering plan — International Telecommunication UnionThe international number format, the 15-digit maximum, and how country codes and national numbers compose.

See private number in the product

Branded caller ID puts your business name on the recipient's screen instead of a bare number. In North America it works through CNAM, the caller-name record attached to a number, combined with STIR/SHAKEN signing that lets the terminating carrier trust the call is really from you.

Explore branded caller idGet early access