UK Numbering Policy

This document defines Ziron’s Policy for the sub-allocation, charging, and management of UK geographic and non-geographic numbers - broadly defined as numbers starting 441, 442, 443, 447, and 448. 

This policy should be read in conjunction with the Ziron Master Services Agreement. The UK National Numbering Plan, as defined by the Office of Communications ('Ofcom'), is available here.



Number ranges are currently allocated to Communications Providers, such as Ziron, by Ofcom in blocks of 100,000 (mobile only), 10,000, 1,000 - or in certain cases - 100 - numbers. At this time, Ziron offers geographic (prefixed 441, 442) numbers ('local'), and non-geographic numbers prefixed 443 ('national'), 447 ('mobile'), and 4480 ('tollfree'). These numbers are then sub-allocated to Ziron customers for use by end users.

Whilst Ziron makes best efforts to provide on demand sub-allocation of numbers to customers, it may, from time to time, not be possible to deliver the requested sub-allocation size without further justification to Ziron and/or Ofcom, or with a delay of between two and four months as further allocations from Ofcom to Ziron are required.

Conservation Areas

Ofcom have designated 600 geographic areas as 'Conservation Areas'. In these areas, Ziron is allocated a block of 1,000 numbers. A small number of areas are designated '100 number block areas', where Ziron is allocated a block of 100 areas. A list of these Conservation Areas can be found in the UK National Numbering Plan

In addition, in April 2013 Ofcom introduced charges to Communications Providers for allocations in 30 area codes, as detailed below.Numbers in these areas may be charged at a different rate to other UK local numbers. Please see the Pricing page on the Ziron Dashboard for details or speak to your Account Manager.

Aberdeen (1224) Middlesborough (1642)
Blackpool (1253) Milton Keynes (1908)
Bournemouth (1202) Northampton (1604)
Bradford (1274) Norwich (1603)
Brighton (1273) Oxford (1865)
Camberley (1276) Plymouth (1752)
Cambridge (1223) Preston (1772)
Colchester (1206) Slough (1753)
Derby (1332) Southend-on-Sea (1702)
Dudley (1384) Stoke-on-Trent (1782)
Dundee (1382) Swansea (1792)
Gloucester (1452) Swindon (1793)
Guildford (1483)  Wakefield (1924)
Hull (1482)  Warrington (1925)
Luton (1582)  Wolverhampton (1902)


Ziron Conservation Areas

In line with Ofcom's Conservation Areas policy or other supply constraints, Ziron has designated some areas with very high demand and/or limited availability as Ziron Conservation Areas, and therefore different charges and/or restricted availability applies. A list of these areas, with alternative suitable areas, are shown below.

Area and Prefix Alternative
London (207) London (203)
London (208) London (203)
Freephone (800) Freephone (808) 


03 numbers

Certain non-geographic ('national') numbers prefixed 443 are subject to restrictions. Details of these are as follows:

030 numbers - designated by Ofcom for use by public sector bodies and not for profit organisations. Ziron may request details of the end user before these numbers can be activated. A list of eligible organisations can be found here.

034/037 numbers - these are specifically to replace previously allocated 084/087 numbers. Whilst Ziron does not directly supply 084/087 numbers at this time, an end user should request the corresponding 034/037 number when porting in 084/087 numbers to Ziron. 

Number Portability

Please see UK Number Portability for further information.

Number Recycling

Please see the Ziron Number Recycling and Quarantining Policy for further information. 


Number Utilisation and Retrieval of Numbers

Numbers sub-allocated by Ziron to a Customer should be used as soon as possible. If a number is no longer required, it should be disconnected via the Ziron API or Dashboard. 

Ziron reserves the right to revoke the right to use number(s) in certain cases, including (but not limited to):

  • Where Ofcom requests the return, cancellation, or suspension of numbers or a number range;
  • If a Customer does not use a number sub-allocated to it within three months of the initial date of sub-allocation;
  • Where Ziron believes a customer is unfairly 'hoarding' numbers, or using methods to give the impression that the number is genuinely being used.
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