P434 Implementation Working Group FAQs


The P434 solution sets out a mandate that the movement of Non-Half Hourly (NHH) Metering System Identifiers (MSIDs) to Half Hourly (HH) should be completed by the Mandate Go-Live Date (currently April 2025).

New UMS MSIDs must be registered directly into the HH Settlement process from 12 months prior to the UMS Mandate Go-Live Date. (set from April 2024). This deadline will also prevent HH UMS MSIDs reverting to NHH Settlement.

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Settlement Dates

Q. What are the Relevant Settlement Dates?

A. They are as follows:

  • October 2023 Industry Data cleanse to start no later than October 2023
  • April 2024 New UMS connections to be HH from April 2024. No reversion from HH to NHH from April 2024
  • April 2025 Target completion date (Milestone 11 (M11) in the Market-wide Half-Hourly Settlement (MHHS) Timetable)

Change of Measurement Class Process

Q. What process maps are available to help visualise the sequence of events for key activities

Q. What is the amended Change of Measurement Class process?

A. The amended Change of Measurement Class (CoMC) process is in BSCP520 ‘Unmetered Supplies Registered in SMRS’ under 3.6.2 ‘Change from Non-Half Hourly to Half Hourly Trading’.

This process applies on or after the date being 12 months prior to the UMS HH Mandate Go-Live Date.

If a customer wants to move from NHH to HH today, the MSID still needs to be disconnected and a new HH MSID needs to be raised as per BSCP520 Section 3.6.1.

If it is 12 months prior to the mandate date in BSCP520, the process changes and requires a CoMC as part of P434. You can follow the existing process today but the earliest you can do a CoMC as part of P434 is currently April 2024.

CP1582 ‘Remove MA from BSCP520’ will make the amended CoMC process clearer and remove ambiguity.

Q. What is the alignment of Metered Indicator (and Connection Type) and Measurement Class?

A. It is best practice whilst performing the data cleanse to ensure that the metered indicator, connection type and visual class are all aligned appropriately. 

Q. Will UMSOs or Suppliers decide which MPANs will go through the COMC process or are to be disconnected?

A. Suppliers will be making the decision on which MPANs are taken forward for Migration

Data cleanse obligations

Q. What are the obligations for UMSOs and Suppliers?

A. The UMSO will need to work with the Supplier to cleanse erroneous or non-existent NHH UMS MSIDs.

The UMSO will need to logically disconnect MSIDs where UMS apparatus no longer physically exists, in consultation with the Supplier. MSIDs should only be logically disconnected if it becomes apparent there is no UMS apparatus connected for the UMS MSID.

Meter Administrators (MAs), Licensed Distribution System Operators (LDSOs), Suppliers, Half Hourly Data Collectors (HHDCs), Non-Half Hourly Data Collectors (NHHDCs) and UMSOs will be mandated to cooperate with each other for the data cleanse and CoMC activities.

There is an obligation for UMSOs and Suppliers to complete the data cleanse template provided by Elexon to facilitate the data cleanse activities. UMSOs and Suppliers should use their best endeavours to complete the template. It is understood that there are scenarios where it will not be possible to complete all fields and scenarios where some fields will be deemed unnecessary.

Once the data cleanse is complete, the Supplier in conjunction with the UMSO, MA and HHDC will migrate its portfolio of NHH UMS MSIDs to HH via the amended CoMC process.

Dealing with orphaned MSIDs is part of the data cleanse activities and these MSIDs should not be disconnected if UMSOs/Suppliers can’t get hold of the Customer.

There is currently no defined term for orphaned MSIDs but the working view is that orphaned MSIDs are MSIDs that should be related but are not related because the MSID data is incorrect and is split across Suppliers.

By the UMS Mandate Go-Live Date the requirement is that all NHH MSIDs have moved to HH by undergoing a CoMC, even if there are still uncertainties or unknowns that need to be dealt with.

Q. What are the obligations for Elexon?

A. This data cleanse activity will be monitored by Elexon, but Elexon does not expect to be requesting or managing data cleanse or CoMC plans.

Retaining, disconnecting and de-energised MSIDs

Q. What do I need to know about MSIDs?

A. The primary MSID within the relationship should be retained and the secondary MSID should be disconnected.

Note that before you can disconnect the secondary MSID you need it to be unrelated. To prevent issues occurring from MSIDs staying in an unrelated state for weeks, timescales should be added to the ‘when’ column in BSCP520 Section 3.6.2, so that once the metering point relationships are removed, the next step happens within a number of days.

If there is a certificate with multiple MSIDs but no relationship flag, they are with different Suppliers.

Q. How does that get resolved?

A. As part of the orphaned MSIDs data cleanse activity, the Suppliers need to agree which MSID will be taken forward.

Q. Is there potential to engage customers with existing HH UMS MPANs to look at merging portfolios?

A. UMSO’s can engage with customers and Suppliers to look at merging portfolios although this could prove difficult at this stage due to some inventories being Half-Hourly and others being Non-Half-Hourly.

It is also worth noting that this activity can also be picked up post-migration.

Q. What is the agreed approach for MPANs which have been de-energised for over a year, should they be disconnected?

A. When completing the data cleanse, consider whether an MPAN should be disconnected. Whilst there are various scenarios an MPAN may be de-energised for over a year with intention to be energised again (E.g. festive lighting), there are some which may be worth checking to be disconnected.

Q. Will the Zero inventory be used for de-energised MPANS?

A. Yes, the Zero inventory should be used for de-energised MPANs such as festive lighting.

Implementation contact lists

Q. Will there be contact lists?

A. Elexon will create Supplier and UMSO contact lists to help facilitate the P434 Implementation.

Please contact [email protected] to request Supplier or UMSO contact details.

Backdating CoMC inventories

Q. What rules/processes will there be around backdating inventories after a CoMC and move to HH UMS has occurred?

Q. Is there a benefit in constraining backdating inventories across a CoMC?

A. It was the consensus of the working group that once an MSID has undergone a CoMC, the inventory should only be backdated to that date.

In preparation for the mandatory HH migration, the Supplier should be responsible for telling the customer that there is a backstop date. It is then the customer’s responsibility to ensure an updated inventory is provided before the CoMC takes place.

This approach will prevent any issues from systems being unable to process backdated inventories with an effective from date prior to the CoMC. It will also prevent the need for additional NHH MSIDs to be created, only to process backdated inventories.

Migration Activities

Q. What is the methodology for migration plans between Supplier, MA, UMSO and HHDC?

A. The migration plan needs to ensure capacity for all roles to manage the required activity. For example, for all roles to manage each CoMC, for the Supplier managing appointments to MA and HHDC and for the UMSO to send D0388 UMS Inventory to MA for the appointment date of the MA. Discussions between all impacted parties needs to take place, so that P434 migration workload can be managed.

Since the UMSO leads a number of migration tasks, it was agreed that it would make sense for each UMSO to build a migration plan that fits with their plans and communicate that out to their Suppliers. This should avoid UMSOs getting inundated with requests from Suppliers.

UMSOs will need to consider contract rounds when building the plan, to prevent resource issues and contractual challenges with customers. These peak periods will need to be agreed between the UMSO and Supplier.

If possible, Suppliers should provide UMSOs with a view of which MSIDs will be required in contract rounds and what volumes will be tied to April or October, to help with resource planning.

Q. Is there a migration threshold per DNO/GSP that is applicable for P434?

A. There are no migration thresholds but there could be processing limitations.

Q. Have DNOs communicated how many MPANs they can process in a day?

A. This has not been determined but as this can be a very manual process, the amount of MPANs that can be processed will depend on resource. 

Q. How do Parties manage and communicate their migration plans?

A. Elexon will work with UMSOs to put together a triage document so Suppliers have a view of UMSO’s workloads over the next 12 months.

However, it is also advised that Suppliers engage with DNO’s and UMSO’s directly to organise their migration dates.

Alongside the proposed triage document, the P434 reporting will also enable stakeholders to see if migrations are being progressed in a timely manner. Under the P434 reporting, Elexon will engage with Suppliers that are behind schedule to understand the reasons for the delay and to help facilitate their progress.

Q. What action will the Performance Assurance Board (PAB) committee take on slow migration progress? Are Suppliers required to submit their migration plans to Elexon?

A. Migrations must be completed by the end of Milestone 11 (April 2025). Until then, no action would be taken as there would be no non-compliance.

The aim of the P434 reporting is to help Suppliers, particularly larger ones, make the expected progress and prompt engagement between PAB and Suppliers to understand any limitations.

Elexon do not require any additional reporting from Participants. All data will be retrieved from the P434 reporting which will come from Elexon’s internal databases.

The P434 reporting can be found here

Data Transfer Network changes

Q. What method of communication should be used in the current appointment process, given the Data Transfer Network (DTN) does not support the role code ‘MA’?

A. Appointment flows should be sent using a pre agreed method of communication, for flexibility. MAs can receive the D0155 over the DTN but the method of communication will not be consistent as some Suppliers prefer to use a spreadsheet or an email.

The historical reason for this is because MA was not defined in that flow as a role, the MA is appointed in place of the MOP where it’s HH UMS. There was no real appetite to force Suppliers to develop new systems to be able to send this flow to a MA over the DTN when it’s going to be replaced by the Data Integration Platform (DIP) under the MHHS programme.

The BSCP520 has always said the “D0155 or equivalent” between the Supplier and the MA. However, the DTC is inconsistent with that. For consistency, it was agreed that a Retail Energy Code (REC) change could be raised for D0155, D0011, D0261 and D0148, to change the recipients and sender, so that it is both known and available to all for optional use.

Process for an unmetered site

Q. Does the HHDC require a D0289 Notification of Measurement Class, Estimated Annual Consumption (EAC) and Profile Class (PC) as part of this process for an unmetered site?

A. BSCP502 requires a D0289 but it does not make any distinction about whether it’s metered or unmetered. Suppliers and HHDCs need to have a bilateral conversation about the flow content.

It is possible to send the flow with the Measurement Class only, as opposed to the PC and EAC as well. Some HHDCs require a D0289 with the Measurement Class only, to stop mismatches at their end.

If the PC and EAC is included in the flow, the HHDC could use this information for data estimation, only if the HHDC has not received any data from the MA. BSCP502 Appendix 4.2 include rules on when the EAC should be used by the HHDC for data estimation purposes.

Q. Will Meter Point Address’ within Electricity Enquiry Service (EES) be updated in line with REC Schedules?

A. REC schedule 29 sets out the Meter Point Address requirements, therefore portfolios should be checked and updated accordingly as part of the data cleanse activities.

Q. Can the awareness of the use of the D0388 UMS inventory and D0388 UMS Inventory Response Flows be confirmed?

A. As of April 2024, all new connections will be HH and will therefore require these flows to be used.

Elexon will liaise with IDNO’s to ensure this has been effectively communicated.

Q. P272 had DCP248 and P432 had DCP414 with these DCP’s aiming to protect consumers from the price change between Non-Half-Hourly and Half-Hourly. Does P434 have a DCP to ensure consumers are protected?

A. A DCP is not required for P434, UMS are all already on the same DUOs/DUNOs tariff regardless of P434.

Data cleanse template: Submitting data

Q. What method should be used for submitting the data cleanse template to Suppliers?

A. It was agreed that the Secure Data Exchange Portal (SDEP) was the best mechanism for submitting and receiving the data cleanse information. However, it was agreed that a specific SDEP category and SDEP title needs to be agreed by the UMSOs and adopted by everyone, so the data can be easily identified. It also prevents the issue of teams not having access to the required areas of SDEP.

SDEP sits in ECOES, so all Suppliers, LDSOs and UMSOs should have access to it. SDEP gets around any GDPR type issues around sharing customer data.

SDEP is best practice but email can also be used, especially for parties that do not have access to SDEP.

Q. Has a specific SDEP category been agreed by the UMSOs and adopted by everyone? 

A. If SDEP is used then the category used should be “Contract Manager Queries” to ensure the appropriate team members have visibility of anything that comes through.

If email is used it is recommended that spreadsheets are password protected in order to adhere to GDPR policies.

If there are any issues with communicating with any Parties, then it is advised to contact your OSM member who will liaise with the Parties on your behalf, alternatively there are this could be escalated via the relevant DCUSA Contract Manager using the DCUSA Contract Manager information on the DCUSA website.

Q. Is it possible to give Suppliers an indication of when information will be required and if it will be the whole list at once or in batches? To help Suppliers plan their part in the activity

A. It is best practise to send the entire list at once, subject to the limitations of Parties IT systems.

The information is required to be returned within the mandated timeframes but it is best practise to provide the response as soon as possible.

If UMSOs do not receive a response within a few weeks, it is advised that the escalation processes are used either directly to the Parties or via the Elexon OSMs if necessary.

Data cleanse template: data quality

Q. Can any type of MSID go in the columns named ‘MSID 1’, ‘MSID 2’, ‘MSID 3’ and ‘MSID 4’ on the data cleanse template?

A. It is best practice for primary or single MSIDs to be included in the ‘MSID 1’ column and child MSIDs to be included in the ‘MSID 2’ column, and so on.

This MSID order will be recommended to avoid parties using different methodologies for collating the information, but it is not mandated due to the following reasons:

  • This order preference was not previously specified, so some data cleanse templates may have already been completed without this distinction
  • Some Suppliers would need to check ECOES for the primary and child MSID relationship, which would require double effort in terms of collating the single MSIDs

Q. Do we need to complete the data cleanse on every MSID or are we only cleansing the related MSIDs and the MSIDs that should be related but might be orphaned?

A. The data cleanse activity includes all MSIDs, but it is accepted that the orphaned MSIDs are going to be the biggest challenge.

Q. How should an UMSO complete the ‘Date of Last Inventory Effective Date’ if the UMSO system only holds a date for the latest EAC change?

A. For this column, impacted UMSOs will either be pulling through migration dates for Change of Supplier (CoS) and Change of Agent events, or effective from dates of genuine inventory updates.

This might be misleading for Suppliers, but genuine inventory updates will mostly be identifiable as bulk CoS and Change of Agent events are public knowledge.

If the ‘Date of Last Inventory Effective Date’ field could include a date for a CoS or Change of Agent event, UMSOs can note this in the proposed additional information column.

This is not an issue for UMSOs that hold the latest inventory effective from date in their systems.

Q. What details are required regarding Columns T and U “Account Issues”?

A. Column T should be used to highlight whether there is an issue or risk with any of the related MSIDs.

Column U should be used to provide further details of any issues, e.g. issues related to invoicing, ownership of the account, etc.

Q. What details are required regarding Column W “Details of last correspondence / contact from the customer”

A. This field should contain any helpful details pertaining to the contact details e.g. whether the customer has been successfully been contacted in recent years or not.

This is an optional field and therefore is not required to be completed if there are no details of value.

Q. What information would be useful in column X “Any other additional useful information”?

A. This is an optional field which could be used to highlight anything the user deems useful e.g. Information regarding any inventories which may need further investigation, or anything out of the ordinary.

Q. How are Primary and Secondary MPANs identified?

A. The Primary MPAN is recorded in the J2243 Data Item within the D0386 flow. The J2243 Data Item is the Primary MPAN in a related MPAN relationship.

Q. What is the consequence of taking forward an MPAN for migration that is not the Primary MPAN?

A. Selecting the Primary MPAN is primarily based on its familiarity within a Related MPAN relationship, offering the advantage of consistency. It was also added that in some NHH portfolios, there are scenarios where you might have a redundant MPAN with a zero EAC which has not been disconnected yet, and a replacement MPAN which has not been registered yet. In this scenario, there is a risk of nominating an unregistered MPAN, which is a data cleanse issue that needs to be cleared up before the COMC.

If you have MPANs that have been de-energised and are no longer required, these should be disconnected as soon as possible as this will avoid confusion going forward.

Q. What steps can an UMSO take if Suppliers will not agree who the Lead Supplier is for MPANs which are split across two or more Suppliers?

A. If an MPAN is split across Suppliers, it is the Supplier’s responsibility during the Data Cleanse to agree on who the Lead Supplier is. If there has been a breakdown of communication, please inform Elexon so Elexon can help facilitate those conversations.

Contacting the customer

Q. Who is responsible for contacting the customer in relation to customer contact details, if further information is required?

A. The Supplier is responsible for contacting the customer in relation to customer contact details and any further clarification or information required.

Q. Where Supplier and UMSO have had no contact with a customer, what are the next steps and who takes the next steps (Supplier or UMSO)?

A. Where the Supplier and UMSO have had no contact with a customer, the Supplier is responsible for trying to establish contact by best endeavours. Please note that the MSIDs need to be migrated regardless of whether contact has been established.

If the UMSO has lost touch with the customer but the customer is paying their bill, the Supplier has an interaction with somebody who is responsible for that MSID. There is an opportunity to share that knowledge to help the UMSO get in touch with the customer.

Equally, if the UMSO and Supplier have lost contact with a customer and the customer is not paying their bill, that information is also valuable to the UMSO, especially if the Supplier has decided to accept that loss.

It was suggested that if this was not complete by migration, it could continue following migration, in which Suppliers could provide UMSOs with a list of outstanding ‘problem’ MSIDs, for the UMSO to try and establish contact with the customer.


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