The 591 Market Message was baselined at version 6.0 as part of the suite of changes to the Retail
Market Design to satisfy new requirements of SEM implementation.
The following will be true for the composition of the 591 Market Message
• One instance of the 591 Market Message will be sent for each Supplier Unit/SSAC
combination.for each Aggregation
• The 591 market message will be checked for each standard profile/DLF combination and if there
are no MPRNs registered for that settlement day, for the combination, then this DLF and
standard profile combination segment will not be populated on the message.

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