How Do You Call Anonymously? The Parts You Can't Learn From Reading

Dial *67 before the full number to place an anonymous call from a US or Canadian line, 141 in the United Kingdom, or #31# on most GSM networks. The recipient's handset shows Private, Blocked or No Caller ID in place of the digits. Under the FCC's rule at 47 CFR § 64.1601(b) the block is free and lasts exactly one call. It changes what the recipient's screen displays and nothing else. The originating carrier still transmits the number, still stores it, and still delivers it to 911, to toll-free subscribers, and to law enforcement holding valid legal process.

What *67 actually sends down the wire

Section 64.1601(b) requires carriers using Signaling System 7 to recognize "*67 dialed as the first three digits of a call (or 1167 for rotary or pulse dialing phones) as a caller's request that the CPN not be passed on an interstate call." CPN is the calling party number. The rule instructs the network to attach a privacy indicator to that number. Nothing in it instructs the network to omit the number. The same section obliges carriers offering line blocking to recognize *82 as the opposite request, and bars any carrier from charging for per-call blocking.

On IP networks the arrangement is visible in the packet headers. RFC 3323 and RFC 3325, the IETF specifications governing privacy in SIP, place the anonymous label in the From header while the genuine number travels in a P-Asserted-Identity header that the terminating network reads and suppresses. Since the FCC's June 30, 2021 implementation deadline, that number is also signed. Under ATIS-1000074, the SHAKEN specification, the originating provider's authentication service builds a cryptographic PASSporT over the calling number, and RFC 8224 sets out how the signature coexists with a privacy request. A blocked call therefore carries a signed, verifiable copy of the number it is concealing.

Jonathan Nelson, director of product management at Hiya and previously product manager for the company's consumer spam-protection product, told the firm's State of the Call Summit that the framework performs unevenly by line type: "It's difficult for a mobile phone call to receive anything other than A-level attestation," he said, while "it's nearly impossible for spoofed calls to get A-level attestation." Attestation measures the originating carrier's confidence about who placed the call, and it is assigned whether or not the number ever reaches a screen.

Why the prefix changes outside North America

3GPP TS 22.081 defines the underlying service as Calling Line Identification Restriction, or CLIR. The specification gives operators two subscription options: permanent mode, where the network restricts every outgoing call, and temporary mode, where the subscriber flips a default per call using the man-machine interface codes in TS 22.030. On a line whose temporary default is presentation allowed, #31# before the number restricts that single call and *31# restores it.

TS 22.081 adds that a subscriber never provisioned for CLIR who attempts to invoke it will have the call setup rejected, which is why the prefix silently fails on some prepaid lines.

British callers dial 141. Ofcom regulates emergency access to 999 and 112 through its General Conditions of Entitlement, but publishes no network-by-network list of 141 support. Reports that the prefix fails on certain mobile virtual network operators, including iD Mobile, come from consumer-guide testing rather than from the regulator, and the GSM code is the documented fallback there.

The three places the block stops working

Emergency lines. Paragraph 64.1601(d) removes the privacy rules entirely for CPN delivery "on a public agency's emergency telephone line or in conjunction with 911 emergency services," for non-public emergency services, and for "any entity's emergency assistance poison control telephone line." A call-taker receives the number and can call back. Ofcom applies the equivalent principle to 999 and 112.

Toll-free numbers. The same rule requires the terminating carrier to honor the privacy indicator "unless the call is made to a called party that subscribes to an ANI or charge number based service and the call is paid for by the called party." Automatic Number Identification is a billing signal that predates Caller ID and travels separately from it. Because the 800, 888, 877 and 866 subscriber pays for the call, that subscriber receives the number. *67 has no effect on ANI.

Unmasking services. TrapCall's support documentation describes the method plainly. The subscriber programs conditional call forwarding so declined, busy and unanswered calls route to TrapCall's platform, which sits behind toll-free numbering and therefore receives ANI. Decline a blocked call and the service rings back with the number attached. It cannot unmask spoofed calls, substitutes a placeholder for VoIP callers using *67, and works only on calls received after activation.

How long the number stays on file

47 CFR § 42.6, adopted at 51 FR 39536 in October 1986 and not substantively amended since, requires every carrier that offers or bills toll telephone service to retain for 18 months "the name, address, and telephone number of the caller, telephone number called, date, time and length of the call." That is a regulatory floor.

Actual practice runs longer and the published figures do not agree. The retention chart prepared by the Justice Department's Computer Crime and Intellectual Property Section with the FBI's Cellular Analysis Survey Team, dated August 2010 and released to the ACLU of North Carolina under FOIA, listed call detail records at one year for Verizon, five to seven years for AT&T post-paid accounts, five years for T-Mobile post-paid and roughly 18 months for Sprint. A 2021 CAST presentation obtained by Property of the People and reported by Motherboard gave AT&T seven years, T-Mobile two years and Verizon one year.

Carriers describing their own practice produced a third set of numbers. In 2015 reporting by US News & World Report, Verizon said roughly one year, AT&T's website said "as long as we need" while a spokesman offered five years, and a T-Mobile spokesman said seven to ten. No source reconciles the three accounts.

AT&T's own Call Trace page supplies one figure that is unambiguous. Records generated by *57 are "recorded at an AT&T location and saved for approximately one year," and "AT&T will only provide trace information to your law enforcement agency, not to you."

Blocking, spoofing and app calling do three different jobs

| | Carrier blocking (*67 / 141 / #31#) | Caller ID spoofing | App calling (WhatsApp and similar) | |---|---|---|---| | Recipient sees | Private, Blocked, No Caller ID | A different working number | Your account number and profile name | | Your carrier's record | Real number, retained | Real number, retained | Data session only; the app holds call metadata | | 911 and poison control | Number delivered in full | Not a lawful route for emergency calls | Most apps cannot reach 911 | | Toll-free line receives | Real number via ANI | The substituted number | Not applicable | | Legal status | Expressly protected by FCC rule | Unlawful with intent to defraud, cause harm or wrongfully obtain value | Governed by the platform's terms | | Cost to caller | Free by rule | Service fee | Data only |

The Truth in Caller ID Act of 2009, codified at 47 U.S.C. § 227(e) with FCC rules at 47 CFR § 64.1604, prohibits transmitting misleading or inaccurate caller ID information with intent to defraud, cause harm or wrongfully obtain anything of value. Section 227(e)(5)(A) sets civil forfeiture at up to $10,000 per violation, up to $30,000 per day for a continuing violation, capped at $1,000,000 for a single act. The RAY BAUM'S Act of 2018 extended that reach to callers originating outside the United States and to text messaging. The FCC normally adjusts these maximums each January for inflation; in Public Notice DA 26-600, released June 17, 2026, the Enforcement Bureau affirmed that no 2026 adjustment would be made, because no October 2025 CPI-U data was produced during the lapse in appropriations that began September 30, 2025. The 2025 levels carry forward for penalties assessed on and after January 15, 2026.

Messaging apps sit outside this framework because they were never anonymous. A WhatsApp account is bound to a phone number, and that number reaches whoever is called. Meta's engineering team documented the Protect IP address in calls setting in November 2023: it relays one-to-one calls through WhatsApp servers so the other party cannot infer location or internet provider from the IP address, at the cost of some latency. Group calls are relayed by default. The setting conceals network metadata and nothing about identity.

What a blocked number does to your chances of being answered

Hiya's 2026 State of the Call report, drawn from a survey of more than 12,000 consumers across six countries, found that 86% of unknown calls go unanswered. The company's 2025 edition put the figure at 80%, and its 2021 report at 94%. Hiya does not publish the question wording behind each year's number, so the swings are better read as a consistently high band than as a trend line.

Landline subscribers can push the rejection rate for blocked calls to certainty. Anonymous Call Rejection switches on with *77 and off with *87 (1177 and 1187 on rotary equipment). AT&T's support documentation describes what the blocked caller hears: an announcement instructing them to hang up, turn off the blocking feature and call again. Calls displaying as Unknown or Out of Area still ring through, because those labels indicate that Caller ID is unavailable on the originating route rather than that the caller dialed *67. Operator-assisted calls also pass.

Why the setting is missing from some handsets

Apple's instructions are Settings, then Apps, then Phone, then Show My Caller ID, switched off. The support page adds the sentence that accounts for most of the confusion around it: "If Show My Caller ID is dimmed or doesn't appear, contact your carrier." The toggle is a network subscription setting, equivalent to permanent-mode CLIR, so it appears only where the carrier exposes it.

Verizon lines, and lines on the former Sprint network and the MVNOs riding on it, commonly lack the row. Verizon's alternative is account-level Caller ID Blocking under Block and Unblock Services in My Verizon, changeable only by the Account Owner or an Account Manager, or *67 before each call. Android implementations vary by manufacturer, generally under the Phone app's calling accounts menu. Because per-line blocking is a subscription state, *82 overrides it for a single call.

FAQ

Does *67 still call anonymously?

Yes. FCC rule 47 CFR § 64.1601(b) still requires carriers using SS7 to honor *67 as a request that the calling number not be displayed, and the block must be free. The recipient sees Private or Blocked. The carrier, 911 and toll-free subscribers still receive the number.

Does *57 actually work?

It records rather than reveals. AT&T states that dialing *57 after a harassing call logs the time, date and number at an AT&T location for approximately one year, and that AT&T will only provide trace information to your law enforcement agency, not to you. It is billed per successful trace.

What does *82 do when calling someone?

*82 unblocks your caller ID for one call. Under 47 CFR § 64.1601(b), carriers offering line blocking must recognize *82 as a request that the calling number be passed. It is the standard way past a line running Anonymous Call Rejection, and it overrides permanent per-line blocking for that call.

What is *77 on a phone?

*77 turns on Anonymous Call Rejection on a North American landline; *87 turns it off. AT&T says blocked callers then hear an announcement telling them to hang up, turn off the blocking feature and call again. Calls marked Unknown or Out of Area still ring through.

How can I call anonymously on an iPhone?

Apple's instructions are Settings, then Apps, then Phone, then Show My Caller ID, turned off. Apple adds that if Show My Caller ID is dimmed or doesn't appear, contact your carrier. Verizon lines commonly lack the toggle and require account-level blocking in My Verizon, or *67 before each call.

Can I call someone anonymously on WhatsApp?

No. A WhatsApp account is tied to a phone number, and that number and profile name reach whoever you call. The Protect IP address in calls setting, documented by Meta's engineering team in November 2023, relays the call through WhatsApp servers so the other party cannot see your IP address. Your number stays visible.