Quote stuffing in power intraday markets under REMIT
Quote stuffing floods a trading system with orders, cancellations or updates to slow other participants down or hide a strategy. In the Spanish decisions, the prize was the first place in the queue when cross-border capacity to France opened.
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The definition
ACER lists quote stuffing among the practices that give false or misleading signals. The CNMC applied it in October 2024 to Gesternova and Axpo Iberia, which sent large numbers of sell orders for the next day's product to the continuous intraday market's processing queue, most of which they knew the system would reject, so that their genuine orders were first in the book when trading opened.
“Quote stuffing: entering a large number of orders to trade and/or cancellations and/or updates to orders to trade so as to create uncertainty for other participants, slowing down their process, and/or to camouflage one's own strategy.”
Why rejected orders count
An order the exchange rejects never reaches the book, so it never shows a price. It can still occupy the gateway in front of everyone else's orders, and the CNMC held that orders the participant knew had no chance of validation were not genuine. Neuro Energía y Gestión's case adds a second element: orders spread across 34 other agents' digital certificates, multiplying the share of the queue one firm controls.
What can explain it innocently
High message rates are normal for algorithmic market making, and a re-quoting strategy can generate many updates per order. The question is whether the messages had a trading purpose. In the Spanish cases the evidence was the rejection rate, the timing against the product's opening, the operator's warnings and the participants' own correspondence.
Decisions
- Gesternova and Axpo Iberia fined for quote stuffing (CNMC, 2024)Spain · Decided 3 October 2024 · Electricity
- Neuro Energía y Gestión fined for controlling the order queueSpain · Decided 24 July 2024 · Electricity
Sources
Sources read on 15 October 2026. This guide summarises the regulation and ACER’s non-binding guidance for orientation; it is not legal advice, and the decisions it cites are the deciding authorities’ findings, some of them under appeal.