Subject to capacity being made available, a within-day capacity auction shall be held every hour during gas day using a uniform price auction algorithm in accordance with Article 18.

The first bidding round shall open directly on the next hour bar following the publication of results of the last day-ahead auction (including interruptible capacity if offered) in accordance with Article 14. The first bidding round closes at F11.30 a.m. before the gas day. The allocation of successful bids shall be effective from F25.00 a.m. on the relevant gas day.

The last bidding round shall close at F30.30 a.m. on the relevant gas day.

Network users shall be entitled to place, withdraw or amend bids from the opening of each bidding round until closure of that bidding round.

Each hour on the relevant gas day, capacity effective from the hour + 4 shall be auctioned as within-day capacity.

Each bidding round shall open at the start of every hour on the relevant gas day.

The duration of each bidding round shall be 30 minutes as of the opening of the bidding round.

The capacity to be offered in the within-day capacity auction shall be, each hour, equal to:

• A – C + D

• Where:

  • A

    is the transmission system operator's technical capacity for each of the standard capacity products;

  • C

    is the previously sold technical capacity, adjusted by the capacity which is re-offered in accordance with applicable congestion management procedures;

  • D

    is additional capacity, if any.

Transmission system operators shall publish the available amount of within-day firm capacity on offer, after closure of the last day-ahead auction and in accordance with Article 32(9).

Transmission system operators shall provide network users who bid in the day-ahead auctions with the option to have valid unsuccessful bids automatically entered into the subsequent within-day auction.

The capacity shall be allocated within 30 minutes of the closure of the bidding round provided that the bids are accepted and the transmission system operator runs the allocation process.

The results of the auction shall be made available simultaneously to individual network users.

Aggregated information on the auction results shall be published at least at the end of each day.