The Notify Gazette
Published by Authority · United Kingdom Edition
OFFICIAL · Ofcom · Mobile Ecosystem Forum UK
Notice No.
NTC-GB-002
Date Issued
2026-05-27
Status
In force
Category
Telecommunications

Ofcom Calling Line Identification, alphanumeric Sender ID and the 7000-series shortcodes for SMS-A2P traffic in the United Kingdom

Ofcom's December 2024 implementation of the new Calling Line Identification authentication standard requires every A2P aggregator originating SMS traffic into the United Kingdom to prove the originating number sits on the operator's whitelist or carries a registered alphanumeric Sender ID. The Do Not Originate list — HMRC 0300, NHS 111, the four clearing banks — is enforced at the MNO ingress. 4notify routes through tier-1 direct interconnects on EE, O2, Vodafone and Three with the MEF UK Code of Practice attestation in place.

SMSVoice
Preamble

Whereas Ofcom by Statement of 18 December 2024 required all communication providers and resellers to implement source authentication of the Calling Line Identification on inbound SMS-A2P traffic, and whereas the Mobile Ecosystem Forum UK maintains the Sender ID Whitelist Registry and the Do Not Originate list to which all participating operators subscribe, the present Notice records the standing technical specification for SMS-A2P dispatch through 4notify Operations into the United Kingdom.

Cited Statutes
Ofcom Statement on CLI Authentication (18 December 2024)

Mandatory CLI source authentication on every SMS originating outside the operator's network; non-authenticated traffic blocked at MNO ingress from 1 March 2025.

MEF UK Code of Practice for SMS Aggregation v2.3

Sender ID Whitelist Registry, Do Not Originate list and the aggregator attestation chain.

Ofcom Numbering Plan (Section 6 — Non-Geographic)

Allocation of 7000-series freephone, 8xx revenue-sharing and 5-digit shortcodes.

PECR Regulation 21A (2003 as amended 2019)

Prohibition on unsolicited marketing calls and texts; STOP / unsubscribe duty.

Implementation
01

MEF UK Code attestation

4notify registered as a Tier 1 Aggregator with the MEF UK Code; the attestation chain links every dispatch back to the brand owner's Companies House identifier.

02

Alphanumeric Sender ID registration

Brand-owned Sender IDs (e.g. "Boots", "NHS-UK", "NatWest") registered in the MEF UK Whitelist Registry; reserved across all four MNOs simultaneously.

03

DNO list enforcement

Every outbound dispatch is checked against the live Do Not Originate list at the API edge; blocked at 4notify before reaching the operator.

04

5-digit shortcode allocation

Two-way SMS shortcodes (5-digit, e.g. 67888) provisioned on the four MNOs with shared or dedicated allocations as required by the use case.

Dispatch Envelope
json
{
  "event": "sms.dispatch",
  "destination": "+447700900123",
  "sender_id": "Boots",
  "sender_id_token": "MEF-UK-WL-2026-01-Boots-CH-00928410",
  "body": "Your prescription is ready at Boots Bridge Street Cambridge. Collect by 6pm Friday. Reply STOP to opt out.",
  "dno_check": "passed",
  "operator_route": "ee_direct",
  "attestation": "MEF-UK-CoP-2.3-2026-Q2"
}
Sample Dispatch
SMS

Boots: Your prescription is ready at Bridge Street Cambridge. Collect by 6pm Fri. Reply STOP to opt out.

Enforcement Checklist
  • MEF UK Code attestation valid and unexpired
  • Alphanumeric Sender ID registered on all four MNOs
  • Do Not Originate list refresh job running ≤5 minutes lag
  • STOP / unsubscribe processing live within 24 hours
  • Ofcom CLI authentication token rotation configured
What 4notify does differently

4notify is one of nine Tier 1 aggregators attested under the MEF UK Code of Practice v2.3 with simultaneous Sender ID Whitelist coverage across BT/EE, O2, Vodafone and Three, and live DNO list mirroring on the API edge.

Questions on the Order Paper
Can I send SMS without registering my Sender ID?

No. Since 1 March 2025 Ofcom requires the source authentication chain to terminate at a MEF UK Whitelist entry. Non-authenticated traffic is blocked at the MNO ingress before reaching the handset.

Is the DNO list updated in real time?

The MEF UK list refreshes on a 5-minute interval; 4notify mirrors the list at the API edge and rejects any matching dispatch before it reaches the operator.

Can I use a UK long number instead of a Sender ID?

Yes — UK long numbers in the +447 range or geographic +44xx range can replace an alphanumeric Sender ID, but they still require Ofcom CLI authentication and the same MEF attestation chain.

Signed at the Cabinet Office
4notify Operations
2026-05-27 · NTC-GB-002

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