Numbering

Expert legal insight into Ofcom’s regulation of UK telephone numbers

What numbering regulation is

Numbering is a core component of the UK’s telecoms regulatory framework. Telephone numbers are national resources that support connectivity, competition and consumer protection across fixed, mobile and IP-based services. Ofcom regulates these resources to ensure efficient allocation, accurate routing, transparent tariffs and the integrity of caller identification information.

Numbering obligations apply to network operators, service providers and other communications providers adopting or using telephone numbers.

Legal basis

Numbering regulation is primarily established under the Communications Act 2003. Ofcom is required to publish and maintain the National Telephone Numbering Plan, set conditions governing the allocation, adoption and use of numbers, and enforce compliance under sections 56 to 63 of the Act.

Key regulatory instruments include:

• the National Telephone Numbering Plan, setting out structure, tariff principles and restrictions
• General Condition B1, governing the use and adoption of numbers
• Ofcom’s CLI Guidance, setting rules for valid and diallable calling line identification
• Ofcom’s Tariff Tables, specifying annual charges for certain ranges

Together these instruments form the statutory basis for numbering regulation in the UK.

How Ofcom manages numbering

Allocation

Only providers of public electronic communications networks or services may apply for number allocations. Applications must demonstrate:

• an appropriate general authorisation
• intended and efficient use of the numbers requested
• capability to route and manage traffic correctly

Allocations are usually granted in blocks of 1,000 or 10,000 numbers and are recorded in the National Numbering Scheme.

Adoption

A number is adopted when it is brought into service on a provider’s network. Providers must:

• maintain accurate internal records
• ensure active utilisation
• return unused numbers where required by Ofcom

Sub-allocation

Providers may sub-allocate numbers to downstream service providers or resellers, subject to record-keeping and compliance with Ofcom’s rules.

Withdrawal

Ofcom may withdraw number allocations where:

• utilisation is insufficient
• allocations remain unused
• numbers are used in a manner harmful to consumers or competition

Structure of the UK Numbering Plan

The National Telephone Numbering Plan sets out the allocation, tariff and service characteristics of each number range.

Geographic numbers (01 and 02 ranges)

Geographic numbers are linked to specific area codes, such as 020 for London. Key characteristics include:

• allocation in blocks of 10,000 numbers or, in conservation areas, blocks of 1,000 numbers
• a requirement to use numbers for subscribers within the relevant area unless tariff equivalence is maintained
• full porting rights between providers

Non-geographic numbers

Non-geographic numbers support national and specialist services.

03 ranges

Tariffed at standard geographic rates and included in call bundles. Widely used by enterprise, public sector and not-for-profit organisations.

055 range

Reserved for corporate and government internal networks and restricted to internal business use.

056 range

Used for location-independent VoIP services. Revenue-sharing is not permitted.

070 personal numbering

Used for personal or follow-me services. Consumer protection rules restrict use to avoid misleading callers into assuming these are mobile numbers.

071–079 mobile ranges

Allocated to mobile network operators and virtual mobile providers. Porting and switching rules apply.

0800 and 0808 Freephone

Calls must be free from both fixed and mobile networks.

084, 087, 09 and 118 ranges (unbundled tariff)

These ranges use the unbundled tariff structure where:

• the Access Charge is set by the caller’s provider, and
• the Service Charge is set by the service provider within capped limits

116 XXX harmonised social-value numbers

Reserved for EU-harmonised social-value helplines, such as:

• 116 000 for missing children
• 116 006 for victims of crime
• 116 117 for medical out-of-hours
• 116 123 for emotional support

Charges and fees

Ofcom charges annual fees for certain number ranges, particularly non-geographic numbers and scarce numbering resources. Fees are set out in the Ofcom Tariff Tables and are designed to promote efficient utilisation and discourage speculative or dormant allocations.

Portability and switching

Consumers must be able to retain their telephone numbers when switching providers. Providers must cooperate to ensure timely and accurate transfers.

Fixed line portability

Portability applies to all geographic numbers, subject to technical feasibility and interconnection arrangements.

Mobile portability

Customers must receive a PAC immediately and port within one working day, supported by relevant obligations under General Condition C7.

VoIP portability

VoIP numbers may be ported where technically feasible and consistent with the Numbering Plan. Providers must avoid practices that lead to unauthorised switching.

CLI validity and number integrity

CLI must be valid, diallable and uniquely attributable. Providers must ensure:

• invalid or spoofed CLIs are blocked where technically feasible
• presentation numbers are allocated legitimately
• CLIs do not mislead or cause harm to consumers

Use of invalid or misleading CLI may constitute persistent misuse and can lead to significant enforcement action.

Special number categories

Emergency numbers

Calls to 999 and 112 must be free-to-caller and supported by resilient routing.

Corporate and legacy ranges

The 055 range is restricted to corporate network use. Legacy data and signalling numbers remain in the numbering system but are closed to new allocations.

Conservation areas and capacity management

In geographic areas with limited numbering availability, Ofcom designates conservation areas. Providers must demonstrate efficient utilisation, and allocations are generally restricted to 1,000-number blocks. Where shortages persist, Ofcom may introduce overlay area codes or move towards national dialling schemes to expand capacity.

Future direction of numbering regulation

Migration to all-IP

The retirement of the PSTN by 2027 will reshape numbering policy. Ofcom is considering:

• modernising geographic boundaries
• enabling more flexible allocation models
• updating routing frameworks for all-IP networks

Next-generation portability

Industry and Ofcom are examining centralised databases and enhanced validation processes to reduce fraud and increase porting efficiency.

International alignment

UK numbering policy continues to align with international frameworks, including ITU-T Recommendation E.164 and CEPT decisions, to support global interoperability.

How Bratby Law assists

We advise clients on all aspects of numbering regulation, including:

• applications for allocation and sub-allocation
• compliance with General Condition B1 and the CLI rules
• numbering strategies for VoIP, cloud and unified communications providers
• tariff governance and consumer information requirements
• conservation area compliance and utilisation auditing
• engagement with Ofcom through consultations, disputes and enforcement action

Why choose Bratby Law

Specialist expertise in regulated communications markets

We combine legal, regulatory and technical knowledge to provide clear, commercially focused guidance on numbering compliance and strategy.

Experience across government, private practice and in-house roles

Our multidisciplinary experience allows us to anticipate regulatory pressures and provide insight into how numbering policy is applied in practice.

Practical and commercially relevant advice

We help providers translate numbering rules into operational processes covering allocation, porting, tariff management and customer communications.

Support across the full regulatory cycle

We advise on initial applications through to enforcement, dispute resolution and appeals, ensuring consistent and informed representation at every stage.

Independent directory rankings

Our specialist expertise is recognised in major independent legal directories:

• Chambers & Partners: Rob Bratby is ranked in the UK Guide 2026 in the “Telecommunications” category: Chambers
• The Legal 500: Rob Bratby is listed as a “Leading Partner – Telecoms” in London (TMT – IT & Telecoms): The Legal 500
• Lexology: Rob Bratby is featured on Lexology’s expert profiles (Global Elite Thought Leader): Lexology

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