ReadMe file for the
UK National Telephone Numbering Plan

This document was obtained from or within the Zip of all the Numbering Plan files It has been converted to HTML to avoid page widening problems.  The layout of Note 6)f) has been improved.
It is preserved here for Section 1) which can be considered the official Obituary Notice for Charge Groups.


Issue 5th April 2004



In order to conform to the National Telephone Numbering Plan (NTNP), the names of the following Geographic Area Codes have changed - 1248, 1268, 1275, 1276, 1291, 1293, 1306, 1322, 1327, 1334, 1344, 1354, 1356, 1375, 1384, 1394, 1425, 1438, 1442, 1451, 1454, 1461, 1470, 1471, 1477, 1478, 1485, 1488, 1489, 1491, 1543, 1561, 1562, 1582, 1588, 1598, 1661, 1668, 1675, 1680, 1681, 1684, 1688, 1689, 1695, 1707, 1720, 1727, 1737, 1744, 1753, 1770, 1784, 1806, 1821, 1856, 1870, 1877, 1883, 1885, 1889, 1895, 1908, 1920, 1922, 1926, 1928, 1932, 1952, 1953, 1963, 1980, 1983, 1984, 1992.


This document describes the lists, as supplied in printed and/or computer readable form, covering the NTNP in the UK.

The files supplied with this ReadMe document are in Delimited Text form .txt and can be imported into a word processor, database or spreadsheet as desired.

The information is Ofcom Copyright © and is published as required by the NTNP. It may be reproduced with due acknowledgement of the source.

Whilst every effort has been made to ensure that the information given in the attached lists are accurate, no legal responsibility is accepted for any errors, omissions or statements in that information.

In particular, the information given on number length in the s1_code.txt list should be regarded as provisional. The information is based on returns from Licensed Operators and is subject to on-going verification. Any queries on the accuracy of the data should be referred initially to the listed Operator.

Enquiries and comments about the documents on this file should be addressed to:-

Numbering Unit,
2A Southwark Bridge Road
London SE1 9HA

Tel:(020) 7783 4153

Fax:(020) 7783 4109


Please do not forward applications for numbering capacity by EMAIL, we require hard copy with an original signature.

The Numbering Unit is unable to advise on the detail of how to set up databases using the files in The data has intentionally been formatted to work in most PC applications.

As a guide: the files are generated from the UK Specified Numbering Scheme which is set up on Microsoft Access 97, running in Windows XP.

Ofcom information is available on the Internet at the following URL:-


The National Telephone Numbering Plan is administered by OFCOM.

File name: sabc.txt

a) Field names: Code,D/DE,Status,Date,Use,Notes,Change

b) Note the area name under the field heading "Use" is based on a list supplied by BT in 1994. The names are consistent with exchange boundary charts maintained by BT. However Operators sometimes use different names for a charge area - OFTEL does not maintain a list of other names that might be in use. Where an SABC range is not in use, it is shown as "Geographic - Unnassigned".

6) S DIGIT 1 LIST (GEOGRAPHIC NUMBERING RANGE, NTNP PART B3) File names: s1_code.txt and s1f_code.txt.


6.1) The files s1f_code.txt and s8f_code.txt contains records at F digit level for those blocks shown as having a 'Mixed' operator in the file s1_code.txt and s8_code.txt respectiveley.

6.2) These files are in Delimited Text form, with text fields having quotation mark " field" delimiters.

a)SABC and DE fields, S1 range
These list all open capacity in the S1 SABC range 1130 to 1999, a total of 91,000 records at DE level and in the S2 range, the DE blocks in the new S2 codes being introduced by NCNC in the range (02SA) 0000 to 1999 but on;ly where the appropriate 02X code is present. Each record relates to a DE block, which is usually 10,000 numbers, except where the local numbers are 5 digit, in which case the DE block is 1,000 numbers.

b) F field
Shows all F digit records for those blocks which are shown as 'Mixed' operator in s1_code.txt.

c)Status field
e.g. Allocated, Reserved, Free, etc. See the Numbering Conventions for definitions. An explanation of the Conventions is given later under Frequently Asked Questions.

d)Date field:
The current estimate of when the protected capacity will become available for re-use. Where dates are shown against Allocated blocks, this is the earliest date the block can be put into service.

This is the identity of the Licensed Operator responsible for managing the allocated capacity. For Reserved capacity the Operator data is usually withheld on grounds of confidentiality. (The Numbering Unit is not in a position to disclose further details of the Operator having Reserved capacity.) The list excludes detail from Manx Telecom, Jersey Telecomms and Guernsey Telecoms, request for such detail should be referred directly to the Operator. The Length field is annotated RTO.

f)Length field:
Number Length Information - this is shown in the "Length" field. This file now lists number lengths as the default figure for the numbering range, without reference to the status of the code, i.e. "Length" is the detail that would apply across the code. In areas of 5 and 6 digit numbering, the default taken is 6 digits.

Please note:

- In numbering areas defined as "Mixed" in the Code List, local numbers can be 5 or 6 digit in length, with a 5 or 4 digit Area code respectively. In these areas, the 5 digit numbers start with the E digit, (annotated 5 + 5) and the 6 digit numbers start with the D digit, (annotated 4 + 6).

- The format of this information is:
                                                       Overall length
Local Number length           Format:Code+number  (excuding the initial 0)
10 digit National dialling (0) +10 10 8 digit (new 02X codes) 2+8 10 7 digit 3+7 10 6 digit 4+6 10 5 digit 4+5 9 5 digit (mixed) 5+5 10 Unusable Not Applicable (N/A) -
g) Change field
Changes since the previous issue -where a record has changed, the "Change" field will be annotated "month-year" This field covers changes from November 1995.

h) Frequently asked questions

- Why can't I load the S Digit 1 file into my spreadsheet? The S Digit 1 file containsover 100,000 records. Many spreadsheets are not designed to handle this quantity, to view the records you may need to load the file into a database or a word processor.

- What database can I use? The files are in Delimited Text format with " " delimiters, and should be compatible with any database that can take this standard.

-How do I find what changes have occurred? Search on the "Change" field.

- What copyright conditions apply? The information is Copyright Ofcom and is published as required by the NTNP. See earlier statement on Copyright.

- What is Allocated status? -numbering capacity designated to the listed Operator.

- What is 'Allocated for Migration only' status? - numbering capacity which was allocated to operators for purpose of migrating their non-conformant ranges.

- What is Reserved status? - numbering Capacity can be reserved in advance of its intended use. When this capacity is required to be put into service, the identity of the Operator is disclosed.

- What is Designated Status? -numbering capacity set aside for a future possible use, e.g. to protect blocks that might be used for migration.

- What is Free status? - numbering capacity which is not allocated at the time of publication of the list.

- What is Protected status? Where numbering capacity has been withdrawn from service, the block or code is sterilised for a period, typically 2 years. Alternatively the Numbering Unit might protect capacity to avoid dialling errors into similar codes.

7) GEOGRAPHIC AND NON-GEOGRAPHIC CODES Files: s1_code.txt, s5_code.txt, s7_code.txt, s8_code.txt, s9_code.txt

These Lists give details on codes allocated as follows:

sabc.txt Summary of S1, S7, S8 and S9 codes, Convention B3

s5_code.txt Corporate Numbering services

s7_code.txt Personal Numbering, Radiopaging and Mobile Services

s8_code.txt Special Services, Convention B8

s9_code.txt Premium Rate Services, Convention B9

The codes are shown without the initial `0'. Area codes are generally 4 digits long, but where this is not the case (eg large cities, like 0121 and 0113 which have 3 digit codes, and some less densely populated locations where the code covers more than one charging area, like 01662 which has both 4 and 5 digit codes) an entry indicating the actual code length appears in the Notes' column. Further detail of code and number length is given in the file s1_code.txt

Where there is no entry in this column (typically for Area Codes), the code is not unique to an individual operator.

This column is for guidance only and gives a general description of the use to which a code is put and does not necessarily reflect any one operator's description or, for Area Codes, the charging area. It is not intended that the description given should establish any convention or replace any existing list.

Additional information is recorded here relating to the code or its use. This may include details of the number of digits in the code (excluding the initial `0'), cross references to other codes, or details of the number of digits in the national number (excluding the initial `0') where this is known to be different from the 10 digit norm of the SNS.

Tariff Notes (s9_code.txt only):
The tariff applying to the 100k range in which the block is situated.


This gives details on Access Codes which are either Allocated, Designated or otherwise used by operators and comprises six columns - plus a check-box - as follows:

All dialled digits of Access Codes are shown.

Access Codes are of three Types :- A, B & C (Numbering Convention B9.7 - June 1994).

"Type A access codes are recognised as having such widely understood significance that they may be used throughout the UK by all operators offering equivalent services (whether directly or through the agency of another operator), and will not be used by any operator for any other service."

"Type B access codes have network-wide significance in that they are used by callers served by one public operator's system to choose services available from that operators system or another public operator's system. To avoid confusion and ambiguity, different type B codes will be allocated to each of the public
operators systems or services needing to be identified for such choice to be
exercised, although it should not be assumed that all services will be made
available to all callers by the operators concerned."

"Type C access codes are set aside for independent use by operators of public telecommunications systems in providing services to customers or operational employees, other than services covered by type A and type B access codes. Operators of different systems have the opportunity to choose corresponding codes where it is convenient and potentially beneficial to adopt a common approach, but are not obliged to do so."

Access Codes that are `Designated' for a particular purpose or used by, but not Allocated to, an operator are shown in addition to those that are Allocated. For Type C Access Codes the use, as notified by operators, is shown in the `Use' column
without a Status being recorded.

Where `Refer to Operator' is shown, this generally signifies a use which is internal to the Operator identified.

This is used to identify Access Code usage which does not conform to the Designation and which will be scheduled for withdrawal (in the disc version this is shown as a column titled `Withdraw').