Quick answer. Ofcom allocates UK telephone numbers to communications providers under the National Numbering Plan. Allocation is conditional: numbers must be used only within the specified range and category, cannot be reassigned to a third party without Ofcom’s consent, and remain subject to Ofcom enforcement. Misuse carries financial penalties and reputational cost, and numbering disputes are expensive because they engage Ofcom’s statutory powers under sections 56 to 58 of the Communications Act 2003.

Numbering regulation appears technical and procedural but carries material legal and commercial consequences. A provider uses telephone numbers allocated by Ofcom to provide services to customers. But the terms of allocation are strict: numbers must be used in accordance with the allocation conditions, cannot be used outside those conditions without Ofcom’s consent, and cannot be assigned to third parties without regulatory approval. Breaching numbering obligations carries reputational and financial risk. More subtly, numbering disputes are expensive to resolve because they engage Ofcom’s enforcement powers.

Trigger situation

A provider needs to acquire number blocks for a new service and must navigate the Ofcom allocation process. A business has received a numbering enforcement notice from Ofcom alleging misuse. Number porting (the requirement to allow customers to switch providers while retaining their numbers) is creating operational or commercial problems. An MVNO or VoIP provider needs to understand its numbering obligations and how they interact with the underlying network operator. A company is acquiring telecoms assets and needs to understand whether number allocations transfer (they do in a share deal but require Ofcom consent in an asset deal). A reseller or channel partner is uncertain about who owns numbers and how they can be used in the business relationship.

Why it matters now

Ofcom has stepped up enforcement on numbering compliance. The volume of number-based fraud, particularly using geographic numbers or non-geographic numbers outside their permitted use, has risen sharply. Ofcom has issued enforcement notices to providers that have used numbers outside the terms of allocation or failed to manage porting obligations properly. The cost of defending an enforcement action, or of remediation where Ofcom finds a breach, is material and often underestimated. Additionally, porting regulation has evolved to tighten timescales: providers must now port numbers more quickly than previously required, creating operational pressure. Finally, the expansion of VoIP and cloud-based communications has created new complexity in numbering, particularly around the assignment of numbers to users and the provider’s obligations to manage that relationship.

Where clients get it wrong

Numbering is treated as an operational matter until it becomes a legal one. The most common mistakes cluster in several areas. First, providers use numbers outside the terms of allocation. Geographic numbers are allocated for a specific area and must be used in that area. Non-geographic numbers (080, 084, 087 ranges) are allocated for specific use classes (customer helplines, information services, premium rate services) and must be used only in that class. A provider that uses 087 numbers for a service other than that for which they were allocated is in breach. Ofcom does not regard this as a technical violation; it regards it as a misuse of the numbering resource.

Second, providers fail to comply with porting timescales and processes. General Condition B3 requires providers to port numbers within specific timeframes (typically 1-2 working days). When a customer switches provider but wants to keep their number, the old provider must port it to the new provider rapidly. A provider that delays porting or places technical obstacles in the way of porting is in breach. Enforcement notices on porting failures are not uncommon.

Third, providers misunderstand the assignment of numbers to end users. Numbers allocated to a provider are allocated to the provider, not to the customers. A provider cannot simply reassign numbers to a customer or reseller as if ownership passes with the use. Ofcom has explicit conditions on how numbers can be assigned to users. A reseller or channel partner cannot use the provider’s numbers as their own. This creates practical issues: if a provider exits a business segment or loses a major customer, what happens to the numbers that customer has been using? The answer is that they revert to the provider, and the customer must be reassigned different numbers. This has commercial consequences and cannot be managed unilaterally by the provider without compliance risk.

Fourth, providers in asset deals assume that number allocations transfer with the business. They do not transfer automatically. In a share deal, the company continues to exist and the number allocations remain with it; no Ofcom consent is needed because the legal entity holding the allocation has not changed. But in an asset deal, where the acquirer purchases the assets of the business rather than the shares, the number allocations do not transfer with the assets. Ofcom’s consent is required. The acquirer must submit a request to Ofcom for transfer of the number allocations. Ofcom will consider whether the acquirer meets the eligibility criteria (which are minimal) and whether any SMP remedies might be affected. In straightforward cases, transfer is routine. But the process has specific requirements and timescales, and a business that failed to seek transfer might find itself operating without authorised numbers.

Fifth, providers underestimate the cost and complexity of managing exceptions to standard numbering rules. Requesting an exception (for example, to use numbers outside the geographic area for which they are allocated, or to use a particular number range for a non-standard purpose) requires formal application to Ofcom. The process is technical and time-consuming. A provider that needs an exception but does not request it, or requests it and is refused, faces either non-compliance or business disruption.

The Advisor’s Perspective

Numbering is the interface where regulatory control meets customer-facing commercial relationships. A telephone number is a valuable asset, and yet it is not owned by the provider; it is allocated by Ofcom under strict conditions. This tension creates disputes. Numbering enforcement actions are disproportionately expensive relative to the sums involved because they are enforcement actions, with all the reputational and financial consequences that status entails. The right approach is preventive: get the numbering framework right at the outset, particularly the relationship between allocation conditions and commercial arrangements with resellers and customers. Understanding who owns numbers, how they can be used, and what happens when arrangements change is essential.

What good looks like

Bratby Law’s approach to numbering has several components. First, we assist with applications for number allocations. We advise on which number ranges are appropriate for your service, help you navigate Ofcom’s application process, and ensure your application is complete and defensible. We advise on the terms of allocation and what uses are permitted.

Second, we establish clear numbering governance. This includes policies on how numbers are assigned to users, how porting requests are handled, what checks are performed before using allocated numbers, and how changes to the service are managed to ensure numbers remain in compliance. We work with your operational teams to embed these policies.

Third, we advise on commercial arrangements with resellers and channel partners. We structure the relationship so that numbering obligations are clear: which party owns numbers, which party is responsible for porting, what happens if the relationship ends. Ambiguity on these issues creates disputes and compliance risk.

Fourth, we monitor your compliance with numbering obligations. This includes periodic audits to check that numbers are being used in accordance with allocation terms, that porting timescales are met, and that regulatory returns to Ofcom are accurate.

Fifth, we respond to Ofcom enquiries and enforcement notices on numbering. We assess the merits of Ofcom’s position, advise on remediation, and represent you in discussions with Ofcom.

Sixth, we assist with numbering aspects of transactions. In asset deals, we advise on Ofcom transfer of number allocations and manage the process. In share deals, we conduct due diligence on the target’s numbering compliance and allocation status.

When to instruct

Some numbering matters are straightforward. A provider using numbers in accordance with the allocation conditions and managing porting properly does not need external input. A provider acquiring a standard number range for an existing service probably does not need specialist input; Ofcom’s application process is routine.

Specialist input becomes necessary in several contexts: (1) a provider is establishing numbering governance for the first time or updating it following a compliance gap; (2) a provider has received an enquiry or enforcement notice from Ofcom on numbering; (3) a provider is using numbers in a non-standard way or needs an exception to the allocation conditions; (4) a provider has a material commercial arrangement with a reseller or customer that depends on numbering, and the arrangement is unclear; (5) an asset deal involves number allocations and you need to understand Ofcom transfer requirements; (6) a provider is uncertain about its porting obligations or is struggling with porting timescales.

How Bratby Law helps

We advise on Ofcom’s numbering regime and which number ranges are appropriate for your service. We assist with applications to Ofcom for number allocations and requests for exceptions or modifications. We establish numbering governance policies and compliance procedures tailored to your operations. We structure commercial arrangements with resellers and customers to ensure numbering obligations are clear and enforceable. We conduct numbering compliance audits. We respond to Ofcom enquiries and enforcement notices on numbering and advise on remediation. We assist with porting process design and troubleshooting where timescales are not being met. We advise on numbering aspects of transactions, including Ofcom transfer of allocations in asset deals and due diligence on numbering compliance in share deals.

FAQs

We are a VoIP provider. How do we acquire numbers for our customers?

You must apply to Ofcom for allocation of numbers appropriate to your service. If you are providing VoIP to business customers, you will typically be allocated geographic numbers (associated with a geographic area). If you are providing services that use non-geographic numbers, you must apply for those ranges. Ofcom will allocate numbers on the basis that you are a VoIP service provider and will have standard allocation conditions. The allocation will specify what use is permitted (e.g. fixed voice service) and how many numbers you can have. Once allocated, you can assign numbers to customers, but the numbers remain allocated to you as the provider. You are responsible for managing porting when your customers switch provider. You cannot sell or permanently assign the numbers to the customer.

A customer wants to switch to a competitor but keep their number. What must we do?

You must port the number to the new provider. General Condition B3 requires you to port numbers within 1-2 working days (depending on the type of number). You cannot refuse, charge a fee for porting, or place technical obstacles in the way. If the customer legitimately acquired the number through you, you must port it. This is a strict obligation and enforcement notices on porting are common. You should have operational processes that handle porting requests promptly and accurately. If you are struggling to meet porting timescales, this is a compliance gap that should be addressed immediately, as Ofcom takes porting compliance seriously.

We use geographic numbers allocated to London for customers in other regions. Is this permitted?

No, not without Ofcom’s consent. Geographic numbers are allocated for a specific area and must be used in that area. Using London geographic numbers for customers in Manchester, for example, is a breach of the allocation conditions. If you have customers across multiple regions, you should apply to Ofcom for numbers allocated to those regions, or you should use non-geographic numbers (which can be used anywhere). If you need to use geographic numbers outside their allocated area, you must apply to Ofcom for an exception. This is possible in some circumstances (for example, for national helplines using a geographic number), but it requires formal application and Ofcom’s consent. Do not assume you can use geographic numbers outside their area without permission.

We are a reseller and our operator-partner has allocated us a block of numbers to use with our customers. Do we own these numbers?

No. The numbers are allocated to the operator-partner, not to you. You are authorised to use them, but you do not own them or control them in the way that an allocated provider does. The allocation conditions apply to the operator-partner, not to you. If the operator-partner withdraws your authorisation or goes out of business, the numbers revert to the operator-partner and your customers lose them. This creates a business risk. You should structure the reseller agreement clearly: specify which numbers you have the right to use, what happens if the relationship ends, and whether you have any protection if the operator-partner assigns numbers to competing resellers. You cannot acquire ownership of allocated numbers; you can only acquire usage rights, and those rights terminate when the agreement ends.

We are acquiring a telecoms business. Do the seller’s number allocations transfer to us?

It depends on whether this is a share deal or an asset deal. In a share deal, you are buying the company that holds the number allocations. The company continues to exist and the allocations remain with it; no Ofcom consent is needed. In an asset deal, where you purchase the business assets rather than the shares, the number allocations do not transfer automatically. The seller must request that Ofcom transfer the allocations to you. Ofcom will consider whether you meet the eligibility criteria (which are minimal) and whether transfer is appropriate. In routine cases, transfer is granted. But you must request it formally, and you should do so before you take over the business. Operating without number allocations is a breach. Ofcom’s process typically takes 4-6 weeks. Budget for this in your asset deal timeline.

Ofcom has issued an enforcement notice alleging we used numbers outside the allocation conditions. What should we do?

Do not ignore it. An enforcement notice is a serious regulatory action. You should seek specialist advice immediately. You need to assess whether Ofcom’s allegation has merit (did you use numbers outside the conditions?) and what the consequences are if Ofcom is correct. Enforcement on numbering can include financial penalties and reputational damage. You should respond to Ofcom with a substantive answer: either accepting the allegation and setting out remediation, or challenging it with evidence that you complied. A weak or delayed response is likely to result in a larger penalty. We can help you assess the allegation, advise on remediation, and represent you in discussions with Ofcom.

Representative experience

Recent and representative matters include:

• Advised a national operator on Ofcom numbering allocation conditions and the management of a large UK number block, including sub-allocation and porting obligations.
• Supported a VoIP provider in obtaining number allocations from Ofcom for the launch of geographic and non-geographic services.
• Advised on numbering compliance in the context of an operator acquisition, assessing transferability of number allocations and porting arrangements.
• Represented a provider in a numbering dispute involving allegations of number misuse and non-compliance with Ofcom’s National Telephone Numbering Plan.
• Drafted numbering management policies for a multi-brand telecoms group to ensure compliance across geographic, non-geographic and mobile number ranges.

Related telecoms regulation pages

See also our other telecoms regulation pages:

• Interconnection regulation
• Ofcom General conditions of entitlement
• Spectrum
• Lawful intercept and the Investigatory Powers Act 2016
• Ofcom Licence Fees
• Code Powers and access to land
• Am I regulated?
• SMP regulation and market reviews
• Telecoms Security
• Ofcom
• Complaints and investigations
• Connected Vehicles and IoT Regulation

Also see

• Why Bratby Law? UK Telecoms Lawyers and AI Lawyers for Regulated Markets
• Services
• Transactions
• Co-counsel
• Fractional General Counsel

Frequently asked questions

What is numbering regulation?

Numbering regulation governs the allocation, adoption, use and portability of UK telephone numbers under the Communications Act 2003 and the National Telephone Numbering Plan.

Who can apply for number allocations?

Only authorised providers of public electronic communications networks or services can apply for numbers from Ofcom.

What are non-geographic numbers?

Non-geographic numbers include 03, 05, 070, 080, 084, 087, 09, 118 and 116 ranges, each subject to specific tariff and service rules.

What are the rules for CLI presentation?

CLIs must be valid, diallable and uniquely attributable. Providers must prevent use of invalid or misleading CLIs and block calls where necessary.

Can Ofcom withdraw allocated numbers?

Yes. Ofcom may withdraw numbers where they are unused, inefficiently used or used in a way that harms consumers or competition.

Independent directory rankings

Our specialist expertise is recognised in major independent legal directories:

• Chambers & Partners: Rob Bratby is ranked as a band 2 lawyer 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 as a Global Elite Thought Leader for data: Lexology

See our Core Communication and TelXL case studies for examples of how we advise on numbering obligations.