REMIT reporting is changing. A new Implementing Regulation, (EU) 2026/256, rewrites what energy firms report to ACER and when. On 29 October 2026, ACER published the first guidance for it. The new rules arrive in three phases, from 29 October 2027 to 1 July 2028. Until then, today's reporting rules still apply.
This guide sets out what ACER published, what applies when, and who reports what. It ends with the new Algorithm ID field, which matters to any firm whose software places orders.
Jordan Dimov (A115). Published 4 November 2026. Checked against ACER's own documents on that date. Sources are at the end. This is a summary for learning, not legal advice.
1. What ACER published on 29 October 2026
The first set covers phase 1. It has five parts:
- The Transaction Reporting User Manual (TRUM), version 8.0. The field-by-field instructions for reporting orders and trades. It has three annexes: lifecycle events, worked examples, and LNG.
- Q&As on transaction reporting. These replace the old FAQs.
- A guideline on transaction reporting. It says who reports what, and when. An annex covers energy derivatives reported under both REMIT and EMIR.
- Guidance on reporting exposure. It has practical examples.
- New XML formats. There are six schemas: standard contracts for electricity and gas, standard LNG contracts, non-standard contracts, electricity transportation, gas transportation, and exposure. All are valid from 29 October 2027.
ACER also published a manual for new market participants, a quick guide for large energy users, a catalogue of changes and an implementation timeline. They are all on ACER's REMIT reporting guidance page.
2. The three phases
| Phase | Applies from | What it brings |
|---|---|---|
| 1 | 29 October 2027 | Continuous reporting of electricity and gas supply, electricity storage and transportation capacity. Exposure reporting. Bilateral contracts with large energy users. LNG market data. |
| 2 | 29 April 2028 | Capacity mechanisms, balancing services, gas storage contracts and gas storage derivatives. Some fundamental data moves to LNG and storage operators. Inside information is reported through inside information platforms. |
| 3 | 1 July 2028 | Hydrogen supply, storage and transportation. |
ACER publishes guidance before each phase. Phase 2 guidance is due by 29 April 2027. Phase 3 guidance is due by 29 October 2027.
Phase 1 in more detail
- Continuous reporting. Standard contracts are reported within two working days (T+2). Non-standard contracts have ten working days (T+10).
- Exposure. Market participants with the obligation report their exposure every quarter. The first report is due on 31 October 2027. ACER can also ask for exposure forecasts.
- Large energy users. A bilateral contract to supply electricity or gas to a single site that can consume 600 GWh a year or more is reported every six months. The first report, for 29 October to 31 December 2027, is due on 31 January 2028. If the contract is concluded on an organised market place, the market place reports it continuously instead.
- LNG market data. Reported as close to real time as technology allows.
3. Who reports
All reporting goes through registered reporting mechanisms (RRMs) and inside information platforms (IIPs). That is true whoever holds the obligation.
- Standard contracts traded on an organised market place: the market place reports them.
- Non-standard contracts: the market participant reports them.
- Exposure: the market participant reports it.
An organised market place is an exchange, a broker platform or a similar venue.
4. Algorithmic trading: the Algorithm ID
ACER's announcement does not mention algorithms. TRUM version 8 does. Field 5 of Table 1 is a new field, the Algorithm ID. It carries "the identification code of the algorithm used for the placing or conclusion of the transaction".
What TRUM version 8 says about it:
- When it applies. It is mandatory when an order or trade on an organised market place involved algorithmic trading, as REMIT defines it. If only people were involved, it is left out.
- Where it applies. It applies to orders and trades on organised market places. It does not apply to bilateral trades. It does not apply to auction markets either, such as the day-ahead auctions.
- One ID per algorithm. The ID must identify the algorithm uniquely within the firm. Two algorithms in one firm cannot share an ID.
- Who assigns it. The market participant assigns it for its own algorithms and for vendor algorithms it runs. The market place assigns it for its own execution algorithms.
- The market place must know it. A market place may require algorithm IDs to be registered before trading. If it does not, the participant still shares the IDs before the transaction is reported.
- It stays the same. The ID appears in the first report of an order and stays the same for the order's whole life.
- A trader is still named. The trader ID stays mandatory. ACER's view is that a human is always responsible for the algorithm.
- The format. The XML element is
<algoId>, up to 100 letters and digits.
A neighbouring field also matters to algorithmic desks. Field 3, liquidity provision activity, says whether an order was part of a market making strategy.
What it means in practice
The Algorithm ID connects reporting to Article 5a of REMIT. Article 5a already asks firms that trade by algorithm to notify the regulator, control and test their systems, and keep records for five years. From 29 October 2027, each algorithmic order or trade on a market place will name the algorithm behind it. A regulator's request for records can then point at one algorithm. Our guide to REMIT Article 5a explains those records.
For trading IT, the questions to answer before October 2027 are practical:
- Which of your systems set an order's price, volume or timing, and so count as algorithms?
- Does each one have a stable, unique ID, kept across versions and deployments?
- How does each market place you trade on want algorithm IDs registered?
- Can your order records carry the ID from the first order event to the last?
5. Dates in November 2026
- 16 November 2026: last day to send questions for ACER's webinar.
- 23 November 2026: ACER webinar on the first set of guidance.
- 27 November 2026: ACER publishes guidance for reporting parties under the Delegated Regulation on RRMs and IIPs, (EU) 2026/255. That regulation requires guidance on authorisation, testing, data validation and security.
ACER also plans to revise its general REMIT Guidance and the Q&As in early 2027. It will hold public webinars in May and November 2027, before the later phases.
Sources
- ACER, "New ACER guidance helps market participants comply with revised REMIT data reporting rules", news item, 29 October 2026. acer.europa.eu
- ACER, REMIT Transaction Reporting User Manual (TRUM), version 8.0, 29 October 2026, data fields 3, 4 and 5. PDF
- ACER, Revised REMIT reporting: implementation timeline, October 2026. PDF
- ACER, REMIT reporting guidance page: the documents and XML schemas. acer.europa.eu
- Commission Implementing Regulation (EU) 2026/256. EUR-Lex