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Glossary · Numbering

What is Restricted number?

  • Also called: restricted call, calling restrictions, restricted caller

Reviewed by Sujan ThapaliyaLast updated

Definition

A restricted number is an incoming call whose caller ID has been deliberately withheld, so the handset shows Restricted, Private or No Caller ID instead of a number. The call is ordinary; only the display of the calling number has been suppressed.
The three STIR/SHAKEN attestation levels, which underpin how restricted 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, restricted number included.

In practice

How restricted number actually works

Withholding happens in one of three ways: the caller dialled a per-call blocking code before the number, their line has caller-ID blocking set permanently, or an intermediate network stripped the identity. From the receiving end these are indistinguishable, which is why there is no reliable way to unmask a restricted call from the handset.

Restricted is not the same as unknown. Unknown usually means the network had no identity to pass — common on some international routes — while restricted means an identity existed and was suppressed. Handsets label them inconsistently, which is the source of most of the confusion.

For a business the practical question is whether to answer them. Blocking restricted calls outright stops a category of nuisance calls and also blocks doctors' surgeries, recruiters and anyone calling from a switchboard that withholds by default.

Worked example

A call that displays Restricted on iPhone may display Private or No Caller ID on Android from the same origin — the label is the handset's choice, not the network's.

Restricted number: common questions

What does restricted mean on a phone call?
That the caller withheld their number. The call arrived normally; only the caller-ID display was suppressed, either per call with a blocking code or permanently on that line.
Can I find out who called from a restricted number?
Not from the handset. Carriers hold the originating identity for their own records but do not expose it to the recipient, and services claiming to unmask restricted calls generally cannot do it either.
Should a business block restricted calls?
Only if you have checked what else it blocks. Switchboards, medical practices and some recruiters withhold by default, so a blanket block can quietly remove legitimate inbound calls along with the nuisance ones.

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 restricted 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