A to Z


You can find information about Amendments and Adjustments in the invoicing section on our Training and education website.

The Central Data Service Provider (CDSP) Annual Charging Statement (ACS) sets out the applicable charges for services provided under the Data Services Contract (DSC).

You will find the current ACS and an archive of older documents on the Joint Office website.

Joint Office website

The Annual Load Profile (ALP) is a parameter defined once a year for sharing out gas each day.

The parameter is specific to each Non-Daily Metered End User Category (EUC) for a given Gas Day. It’s the proportion of its Annual Quantity (AQ) that a site in that EUC is expected to use on that day expressed in terms of 365th shares of the AQ.

The ALPs are set before the start of the Gas Year and are used for calculating NDM Demand Estimation.To find an ALP for a given year, please visit UK Link Secured Documentation. *

(Then folder 18. NDM Profiling and Capacity Estimation Algorithms/choose Gas Year/folder 3. Demand Estimation Parameters/folder b. Demand Estimation Supporting Files)

*Access to secure links are only available to gas shippers and transporters. To gain access find out about accessing secure documents.

The AQ is a value which represents the amount of gas (in kWh) that a site will use in the coming year under normal seasonal weather conditions.

An AQ Correction is a process to request a revised Annual Quantity (AQ) in a small list of exceptional circumstances.

The Xoserve Annual Review details our progress, achievements and the challenges of the previous year.

This was previously called the Annual Report. 

Find our Annual Review on our dedicated webpage.


Billable Meter Readings (MBR) is a file type that is sent from Xoserve to Shippers containing Meter Readings for Supply Meter Points within their portfolio.

Typically, the MBR file is used to notify Shippers of Must Reads and Meter Readings estimated by Xoserve (such as Opening Meter Readings at Change of Shipper events).

Billing is part of Xoserve operations. To see all key invoice dates, view our latest billing and invoicing calendar.

Find out more about invoicing on our Invoice type, charges & VAT page.

Our billing calendar details all the scheduled billing and payment dates for invoices relating to transportation, energy and our role as Central Data Service Provider (CDSP).

Our budget is part of the business planning process.

Learn more about our business planning process on our dedicated webpage

Our annual business plan defines our budgets and direction through an engagement process with customers.

Learn more about our business plans and planning process.


The Calorific Value is a multiplier indicating how many kWh of energy is obtained from one cubic meter of gas. It’s measured each day* and can vary from day to day and between different areas of the GB gas network.


*Access to secure links are only available to gas shippers and transporters. To gain access find out about accessing secure documents.

You can find information about Local Distribution Zone (LDZ) Capacity and Commodity in the invoicing section on our Training and education webpage.

The information includes the Formula Year Annual Quantity (AQ)/Supply Off-Take Quantity (SOQ) Timeline and Charge Types.

Capped is a Meter Status that indicates the meter is not currently consuming gas because the meter point is physically capped.

Be part of a talented and diverse team that’s transforming the gas energy market for our customers and consumers across Britain.

Find out more on our Why join Xoserve? page.

As Central Data Service Provider (CDSP), Xoserve uses Change Packs to invite industry opinion to be registered and shared relating to solution options and the design of potential changes to gas central systems or processes.

Change Packs are hosted on the Xoserve website, with organisations made aware via email when a new one has been published.

Learn more about How we manage change.

As Central Data Service Provider (CDSP), Xoserve is responsible for the customer change register.

The customer change register lists all change proposals that are either in delivery, in capture or have recently been implemented.

For queries relating to the content of the register, email uklink@xoserve.com.

A Check Read is related to a read recorded because of a site visit or meter update. This results in a special reconciliation from the previous Check Read to the current Check Read.

A Class 1 site has an Annual Quantity (AQ) of 58.6 million kWh or above and has a mandatorily daily read by a daily meter service provider (DMSP).

A Class 3 is a site that’s specified by the shipper to receive reads in weekly batches.

The CWV is a blended measure of actual weather on a day.

The weather items that make up the CWV and the formula are managed by the Demand Estimation Sub-Committee. They are published in the annual NDM Algorithm booklet which can be found on UK Link Secured Documentation. *

(Then folder 18. NDM Profiling and Capacity Estimation Algorithms/choose Gas Year/folder 4. NDM Algorithms booklet)

*Access to secure links are only available to gas shippers and transporters. To gain access find out about accessing secure documents.

A Confirmation File (CNF) is a UK Link file type and part of Xoserve’s Supply Point Administration (SPA) operational process.

A CNF is sent from Shippers to Xoserve confirming (or cancelling the confirmation) ownership of an end consumer supply.

The file also enables the Shipper to specify settlement information and provide details related to the end consumer.

A Connected System Exit Point (CSEP) is the exit point from a large distribution gas network (DN) to an Independent Gas Transporter’s (IGT) network.

There is no meter at the exit point which is owned and managed by the IGT.

Our Contact Management Service is an online business-to-business tool for processing contacts to and from us.

You can use the CMS to:

  • update Meter Point Reference Numbers (MPRNs) in your portfolio
  • request an update to your consumption data
  • manage Theft of Gas (TOG).

Correla is the name of a new independently owned company that Xoserve has created in response to the transforming energy market.

As a product-orientated technology and data services company, Correla delivers services back to Xoserve through a commercial contract.

The separation of the two companies took place in April 2021.

A Customer Amendment Request File (CNC) is a UK Link file type and part of Xoserve’s Supply Point Administration (SPA) operational process.

A CNC is sent from shippers to Xoserve updating consumer information such as their contact details or priority services status.

Our Customer Expert Day is a dedicated training day for customers that covers specific industry processes.

The content of training days varies, depending on demand of customer type (e.g. Shipper or Independent Gas Transporter) and process focus area (e.g. Supply Point Administration, Meter Reads or Annual Quantity processes).

Learn more about our Customer Expert Day in Training sessions.


The aggregated Daily Biomethane Injections Report was introduced by XRN 5183 to provide visibility of historical and current daily biomethane injection statistics.

This information informs future biomethane projects and helps increase the use of biomethane in the energy industry.

You can download the monthly Daily Biomethane Injections Report from our dedicated Decarbonisation webpage.


The DDP is an Xoserve online tool for sharing a range of data and insights with customers.

Following the launch of the Central Switching Service (CSS), the DES has now been replaced by the Gas Enquiry Service (GES)

The GES is a tool for completing gas market enquiries that are critical to the daily running of the industry. 

The UK Link Data Permissions Matrix is the register (in Excel spreadsheet format) of data items held in our Central Data Service Provider (CDSP) systems that each customer type is entitled to access.

View the UK Link data Permissions Matrix on our UK Link System webpage.

DSC Credit Committee Rules detail credit management obligations for DSC customers.

System defects can potentially impact our services and have been discussed historically as part of our Issue Management responses.

Customer impacting defects are logged on the Issue Register and details to resolve/track these are covered by the DSC Delivery Sub-Group (DSG).


The DSG is a monthly meeting facilitated by Xoserve to collaborate with Data Service Customers (DSC) on change solutions and design.

The DSG acts as an advisory group to the DSC Change Management Committee (ChMC).

DNs are the five large Gas Networks that provide gas to homes and businesses in Britain.


The EUC is the group in which each site is placed for demand attribution, Unidentified Gas sharing and invoicing purposes because they have similar patterns of demand.

The EUC is determined by location (Local Distribution Zone) and Annual Quantity. In some cases, by type of sites (domestic v industrial/commercial) and billing type (prepayment/credit), or the amount of winter usage compared to the total Annual Quantity.

The CNU Charge Type is the neutrality charge for all Energy Balancing charges (cashout, scheduling and Trades) incurred for the current month.

When adjustments are made to previously invoiced charges, the adjustment to the original neutrality charges are processed via the ARS Charge Type.

Discover more

Energy Balancing Neutrality Charges are shared out based on your daily throughputs, excluding trades as a share of all users' throughputs.

Discover more

A calendar that shows key industry forums, events and Xoserve training delivery dates.


File Formats are documents that outline how to compile a file to be submitted to our systems, i.e. UK Link, Contact Management Service, Gemini.

Find my Supplier is a web service that enables the user to find out who their gas supplier is as well as their meter point reference number and gas transporter.


The Gas Enquiry Service is a tool for completing gas market enquiries that are critical to the daily running of the industry. The GES replaced the Data Enquiry Service (DES) on 18 July 2022.

Gas Shippers contract with Gas Transporters to move gas through the gas pipeline network on behalf of a Gas Supplier.

Gas Shippers must have a valid Gas Shipper Licence issued by Ofgem before engaging in gas shipping activities.

  There are 3 classes of Shippers:

  • Class A (>1 million sites)

  • Class B (< 1 million sites, majority commercial)

  • Class C (< 1 million sites, majority domestic).

Gas Suppliers contract directly with the gas consumer to provide them with gas and gas metering services.

Gas Suppliers are responsible for maintaining the details attached to the Meter Point Reference Number (MPRN) for the supply.

All Gas Suppliers have an associated Shipper, who move the gas on their behalf.

GTs maintain and operate the pipes and networks that provide gas to homes and businesses throughout Britain.

GTs include the Transmission Service, Distribution Networks (DNs) and Independent Gas Transporters (IGTs).

Information about the Application Programming Interfaces (APIs) available within the Gemini system can be found in the Gemini Technical Documents.

A glossary of industry and Xoserve terminology.


IGTs are companies that develop, operate and maintain a network of pipes that supply gas in a local network.

All IGTs local networks will ultimately be connected to one of the large Gas Distribution Networks, either directly, or indirectly via other IGT networks.

IX is the communications system used for transferring user files between Gemini, UK Link and our customers.

Xoserve manages many invoicing processes across different industry participants, but broadly, these can be split into two areas:

  1. The invoices Xoserve issues to our Data Services Contract (DSC) customers to pay for the DSC services we deliver. These are issued to Shippers and Transporters, which includes National Gas Transmission, Distribution Networks and Independent Gas Transporters (IGTs).

  2. A section of our operations is dedicated to delivering gas transportation Invoices to the Shipper community, on behalf of National Gas Transmission and the Distribution Networks.


Jargon buster refers to our glossary of industry and Xoserve terminology.

Be part of a talented and diverse team that’s transforming the gas energy market for our customers and consumers across Britain.

Find out more about why join Xoserve.


The Line in the Sand is the gas industry’s common term for the Code Cut Off Date (defined in the Uniform Network Code (UNC) General Terms – Section C). This limits the duration of retrospective charges and credits, to give all parties more certainty on historic energy bills.

The Line in the Sand is currently reset annually to a date three years in the past, and rolls forward once a year on 1 April, to simplify the changes for all parties. Therefore, the Line in the Sand is always a date between three and four years in the past.

This means that no retrospective adjustments can be processed for periods before that date (once the March Amendment Invoice has been issued in late April each year).

Where a proposed adjustment or reconciliation spans the Line in the Sand date, only the post-Line in the Sand portion will be charged/credited, and any earlier periods will not be corrected, leaving the previous billed/reconciled position unchanged.

The invoicing system calculates the energy for the whole period, using the start and end dates, but splits it on the prevailing Line in the Sand date.

The List of Organisations is a list of organisations that are active on UK Link Systems.

A LDZ is a portion of the country ‘owned’ by a specific gas transporter to determine the area for which they distribute gas.

You can view this map to find out your LDZ area.

A Local Security Officer(LSO) is a nominated person within an organisation that provides a single point of contact on UK Link security matters.

A LSO is responsible for the management and authorisation of all requests to add, amend or remove access to UK Link, Gemini, Xoserve Service Portal and the Contact Management Service within their organisation.

If you don’t know who the LSO is in your organisation, please raise a support request.


The Market Domain Data (MDD) Market Participant Identity List is a list of gas market participants which defines and controls the Short Codes used to identify an organisation in the industry.

The list can be used to identify gas market participants in industry messages including those processed by the Central Switching Service (CSS).

You can download the latest MDD list from our Market Domain Data (MDD) webpage under the heading ‘MDD Market Participant list’.

A MSC is a gas industry indicator used in industry flows to specify whether a site is used predominantly for domestic or industrial/commercial (I&C) purposes. The valid entries are D and I.

It’s also sometimes referred to as the Market Sector Flag (MSF).

Market Trials are required for some changes that are made to gas central systems or processes to ensure they are safely implemented.

These trials involve multiple industry parties testing the proposed functionality before it’s implemented in IT systems.

For media enquiries, please email press@xoserve.com.

A Meter Asset Manager is a company that is appointed by the gas supplier to manage the gas measuring equipment (meter or corrector) attached to their site.

Meter Models are the approved values for asset/device data.

Learn more about these values on the Supply Point Administration Agreement (SPAA) website.

A MPRN, also known as a M Number or Meter Number, is a unique number that relates to a site. The six- to 10-digit number appears on every gas bill in Britain.

MPRNs are created through our M Number Creation (MNC) service.

A MPRN can only be created for a Live Supply Meter Point where there is no live UK Link record.

Must Reads are a process where a read hasn't been provided by a shipper for a set period and a site visit is triggered to obtain a read.


Nomination relates to either nominations for transfer of ownership or gas nominations within Gemini.

Non-Standard Sites (formerly known as Unique Sites) are large consuming industrial sites that are managed differently to other Meter Point Reference Number (MPRN) sites.

Due to consumption volumes and related financials, these can often be very high priority to customers.

NRL is the file extension for an automated information file from Xoserve to Shipper to advise them of their new Annual Quantities which will go live the following month.

The NRL is the umbrella file, but it’s made up of thousands of individual records, depending on the transactions for the month.

The NRL hierarchy shows the possible records that could be present - see individual file record formats for the content and layout.*

The file is only issued if there are transactions to report - there is no nil return report.

*Access to secure links are only available to gas shippers and transporters. To gain access find out about accessing secure documents.


Our address is Xoserve Limited, 65 New Road, Solihull, B91 3DL

You can find directions and parking information on our dedicated Address and directions webpage.

The Off Gas Postcode Register is a list of postcodes where Xoserve holds no record of an active gas connection by either large or small gas transporters.

You can download the current Off Gas Postcode Register from our dedicated Supply Point Administration (SPA) webpage.

Visit Supply Point Administration (SPA) webpage


Portal is a web-based application that allows customers to directly update UK Link in certain circumstances.

A postcode is a code relating to a certain geographical location.

You can find a mapping of GB postcodes to gas Local Distribution Zones (LDZs) in the Postcode Exit Zone List (.zip file).

This list is created by the Network Operators.

Principles and Approach is part of our business planning process.

Priority Consumers are certain gas Supply Meter Points (SMPs) for Industrial and Commercial sites. During a national gas emergency, these sites are lower on the list of sites that are directed to cease taking gas. 

This is set out in the Uniform Network Code, section Q1.7.1.

SMPs on the Priority Consumer List are the last to be told to cease taking gas where necessary for safety reasons. 

Find out more on the Priority Consumers page. 

This process is separate from the consumer-targeted Priority Services Register, which you can learn more about on Ofgem's website.

The Priority Services Register is a multi-utility service that provides support to people in vulnerable situations. 

This is for domestic consumers only and you will need to know who your energy supplier or network operator is before applying. 

You can find out who supplies your gas by using our Find My Supplier service. 

To find out more about the Priority Services Register, visit the Ofgem website.

This service is separate from the Priority Consumer process, which you can find out more about on our dedicated webpage.  

A Profile Allocation File (LPA) is a file type for an invoice sent from Xoserve to Shippers that contains the reconciliation factor.


*Access to secure links are only available to gas shippers and transporters. To gain access find out about accessing secure documents.

Project Nexus was a gas industry project that was implemented in June 2017.

The project developed industry requirements for changes to gas settlement arrangements and implemented new central systems and processes to support those arrangements.

Business Requirements documents and meeting minutes can still be found on the Joint Office website.


A RD1 is a file type that is sent from Meter Reading Agents to Xoserve containing information on a site visit.

Reads are taken from meters and uploaded against Meter Point Reference Numbers (MPRNs) to calculate gas consumption.

This is a monthly report of the total amount of reconciliation energy which has been processed since the introduction of new settlement arrangements in 2017. The report is summarised by End User Category, invoice month and the estimated original month of the allocation.

Some industry parties use it to understand trends in Unidentified Gas due to reconciliation.

You can download the Reconciliation by Month report from the Useful Links section on our Unidentified Gas (UIG) webpage.

Reconfirmation is a process where a shipper in ownership submits a confirmation to update the details of their ownership.

The Meter Read Frequency (MRF) for Supply Meter Points with an Annual Quantity (AQ) above 293,000 kWh must be set to 'M' – Monthly.

If the field is set to anything other than Monthly for Class 3 or 4, the request will be rejected with rejection code MRF00012.

View the list of Shipper Rejection Codes.*

*Access to secure links are only available to gas shippers and transporters. To gain access find out about accessing secure documents.

Rejection codes are a list of codes that are generated when a file is rejected from our system.

A RGMA is instigated when assistance is required with a Meter Exchange or updating meter details on our system to correct an erroneous Read history.


A SC9 is a file type that is sent to Shippers and contains information on Calorific Values.

A Composite Weather Variable (CWV) is a blended measure of actual weather on a day. A Seasonal Normal Composite Weather Variable (SNCWV) is updated every few years.

The current values of the SNCWV can be found in UK Link Secured Documentation. *

(Then folder 18. NDM Profiling and Capacity Estimation Algorithms/choose Gas Year/folder 3. Demand Estimation Parameters/folder b. Demand Estimation Supporting Files)

*Access to secure links are only available to gas shippers and transporters. To gain access find out about accessing secure documents.

All key Data Services Contract (DSC) and Central Data Services Provider (CDSP) service documents can be found on the Joint Office website .

The CDSP Service Line Description Table documents detail all service lines the CDSP delivers; if/how they align to Uniform Network Code and any relating industry Change Modification references.

The service desk is where technical issues can be logged with Xoserve.

'Service Lay Additional Information' could refer to a variety of information including:

  • the date/year that the service was installed
  • any quotation number that the customer may have received
  • a development project reference
  • the organisation that installed the service, e.g. the network, a Utility Infrastructure Provider (UIP) or an Independent Gas Transporter (iGT).

Our three Service Portals provide access to UK Link, the Gas Enquiry Service (GES), and Contact Management Service (CMS).

You can access the individual Service Portals via a link on the UK Link Systems, GES and CMS webpages.

The Shipper is a company that buys and sells gas and arranges for its transportation through networks owned by gas transporters.

Find out more about how to become a Shipper by watching this video and register to Join/exit the gas market.

Further information is also available by emailing Xoserve.

Shipperless is a site that does not have a shipper associated with it.

The Supply Off-Take Quantity (SOQ) is the highest daily quantity of gas (in kWh) the site is expected to use in a day under 1-in-20 peak day conditions.

For Non-Daily Metered sites, it is derived from the AQ, using the Peak Load Factor and the formula SOQ = AQ/ (PLF x 365).

For Daily Metered sites, the SOQ is the highest consumption figure in the previous or current winter.

Switching is the term used to describe the transferring of ownership of a Meter Point Reference Number (MPRN) from one gas shipper to another.

At Xoserve, this is completed via the Confirmation Process, where the new Supplier will instruct their Shipper to transfer the MPRN onto their portfolio.

Switching could also refer to the Switching programme (CSS).

SwitchStream is an Xoserve adaptor product to support customers to interface with the Central Switching Service (CSS).

The tool takes information from gas and electricity customers and translates that information into CSS-compatible formats to manage switches.


Theft of Gas is a scenario where a meter worker or consumer has found an illegal bypass, or a meter that has been interfered with, resulting in unpaid gas consumption.

You can manage Theft of Gas using the Contact Management Service (CMS).

This is a section on the Xoserve website called Training sessions that houses all our training materials and training calendar.

You can find information about Transmission and Energy Balancing Invoices and Validation within Invoice type, charges & VAT.

The information includes National Transmission System (NTS) Entry Capacity and NTS Exit Capacity.

You can find the rates for Distribution Network (DN) transportation charges (latest and historic) and National Transmission System (NTS) transmission charges (latest and historic) on the Joint Office of Gas Transporters’ website.


UK Link is the recognised name of the suite of central gas systems maintained by Xoserve in our role as Central Data Service Provider (CDSP).

The UK Link Manual* sets out the standards and policy for using core systems such as Gas Enquiry, UK Link, and Gemini.

*Access to secure links are only available to gas shippers and transporters. To gain access find out about accessing secure documents.

A UMR is a Meter Read for a Class 4 site that can be submitted annually, 6 monthly or monthly.

Unidentified Gas (UIG) is gas that is consumed within a Local Distribution Zone (LDZ), but not attributed to an individual Supply Meter Point or accounted for as Shrinkage.

UIG is measured in kWh for each Gas Day and LDZ.

Xoserve provide urgent notifications about suspicious UIG levels.

Uniform Network Code (UNC) is the framework between Gas Shippers and Transporters that enables the effective functioning of the UK gas industry.

The UNC Document describes the basis on which Gas Shippers are able to enter gas into, and extract it from, the gas transmission and distribution systems.


The Winter-to-Annual Ratio is the ratio of the amount of gas that a larger site uses in the winter months compared to its total Annual Quantity (AQ).

The Winter-to-Annual Ratio is expressed as a percentage and will be assigned to one of four bands (ranging from high to low), which helps determine which End User Category (EUC) the site is assigned to. The higher the WAR Band, the more gas the site uses in a typical winter, and this will be reflected in the Annual Load Profile for that EUC.

To find the Winter-to-Annual Ratio band thresholds for a given year, please visit UK Link Secured Documentation.* 

(Then folder 18. NDM Profiling and Capacity Estimation Algorithms/choose Gas Year/folder 3. Demand Estimation Parameters/folder b. Demand Estimation Supporting Files)

*Access to secure links are only available to gas shippers and transporters. To gain access find out about accessing secure documents.


‘You Said, We Did’ was a feature in our Customer Matters publication that we used for customer feedback to improve our service.