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 The Day-Ahead and Intraday Market 



The Day-Ahead Market (DAM) is a single pan-European energy trading platform in the ex-ante time frame for scheduling bids and offers and interconnector flows across participating regions of Europe. The DAM involves the implicit allocation of cross-border capacity through a single centralised price coupling algorithm (EUPHEMIA). The algorithm, taking into account the cross-border capacity advised by the TSOs, determines prices and positions for all participating participants in all coupled markets.

The Intraday Market (IDM) allows participants to adjust their physical positions closer to real time, based on more up to date information for trades to occur. The SEMOpx IDM consists of three auctions and a continuous trading market which runs up to an hour before real-time.

How Does It Work?

The DAM is operated by Nominated Electricity Market Operators (NEMOs) in each bidding zone or geographical region. In the SEM bidding zone (the island of Ireland), EirGrid has been designated as a NEMO for Ireland, and SONI has been designated as a NEMO for Northern Ireland. EirGrid and SONI will operate as SEMOpx in their roles as NEMO for the DAM. 


SEMOpx is responsible for registration of participants, market systems operation (excluding running EUPHEMIA), settlement, credit risk management, currency risk, and access to market data.  Participants submit bids and offers to SEMOpx, who acts as the central counterparty to all trades—that is, participants buy and sell from SEMOpx (the NEMO) rather than from each other. SEMOpx interacts with the Market Coupling Operator (MCO), who runs the EUPHEMIA price coupling algorithm. The market trading system for the SEMOpx DAM is provided by EPEX SPOT and settlement services are provided by European Commodity Clearing (ECC) under contract to SEMOpx.

Who Can Participate?

To trade in the SEMOpx DAM and IDM you must have, or be allowed to trade on behalf of, a unit in the Balancing Market. Participation in the IDM and DAM is not mandatory, but they are the only ways of achieving an ex-ante position in the SEM, which is the mechanism through which participants establish their physical position to minimise their exposure in the Balancing Market.

SEMO provides an Agent of Last Resort service to assist small or intermittent generators to participate in the IDM and DAM by making submissions to a NEMO on their behalf.

How To Register?

Existing SEM Participants and new SEM Participants that are looking to be involved in the I-SEM Market Trial will need to complete the SEMOpx Transitional Registration Forms. Otherwise, please complete the standard SEMOpx registration forms. 


A SEMOpx registration guide is included with the registration packs and will provide an explanation for each form, its significance, the submission format required, and a due date for each returned form.  Please refer to the relevant registration guides with initial queries.

Information is also included in the registration guide regarding registration with ECC who provide the clearing and settlement services for the SEMOpx Day-Ahead and Intraday Markets.

Please see the Registration Process
here and the SEMOpx Transitional Registration and Standard Registration Forms can be found here.


Important! Participants are strongly encouraged to submit their applications as early as possible. In particular, registration for the DAM and IDM involves meeting ECC “Know Your Customer requirements” and contracting a Clearing Member/Settlement Bank which can take a number of months to complete.

What Are The Costs?

Please see SEMOpx Statement of Charges detailing the once off entry fee, annual subscription fee, the variable DAM and IDM trading fees and the fees for additional user logins for the M7 and ETS systems.

Further Information

For further information on SEMOpx please review to the following document(s):

*Please note, any revisions to dates and deadlines are detailed in the Transitional Registration Plan.

Contact Details

If you have any questions in relation to the above information, please contact us through the following means:

Email Correspondence:

SEMO is a joint venture between EirGrid PLC and SONI Limited