MiFIR transaction reporting: fields and the reporting chain.

Which transactions are reportable

Article 26 of Regulation (EU) No 600/2014 requires investment firms that execute transactions in financial instruments to report the details to their competent authority. Two tests have to be satisfied together, and firms routinely get one right and the other wrong.

• The instrument test. Instruments admitted to trading or traded on a trading venue, or for which a request for admission has been made — plus instruments whose underlying is such an instrument, and instruments based on baskets or indices whose components are.
• The transaction test. Defined in the technical standards rather than in ordinary language. The conclusion of an acquisition or disposal is a transaction; so is a simultaneous acquisition and disposal with no change in ownership where post-trade publication is required. A number of events that look like transactions are excluded.

Branches complicate the perimeter further: a branch has no separate legal personality, so transactions executed through non-Union branches of Union investment firms are within scope, and Union branches of third-country firms carry their own treatment.

Who reports, and the chain

Reporting is single-sided — unlike EMIR, only the investment firm reports, and there is no counterparty report to reconcile against. Reports go to the competent authority of the home member state, either directly, through an approved reporting mechanism, or through the trading venue where the transaction was executed on that venue.

Where a chain of firms is involved, the framework decides which of them reports rather than leaving it to commercial agreement. A firm transmitting an order can pass the required details to the receiving firm so that the receiving firm reports, but only if the transmission meets the conditions set out in the standards. If it does not, the transmitting firm reports for itself. Getting this wrong produces either duplicate reports or a gap, and both are supervisory findings.

The field groups

The reportable fields are specified in Delegated Regulation (EU) 2017/590 — commonly called RTS 22 — and run to more than sixty. They fall into six groups.

The decision and execution fields are what make this a market abuse framework rather than a settlement one. They require a firm to be able to attribute every reportable transaction to a named individual or a registered algorithm, which is a governance problem before it is a data problem.

Identifiers and reference data

Every legal entity in a report is identified by its legal entity identifier, and a firm cannot execute for a client that does not have one. Natural persons are identified by a concatenated national identifier constructed to a prescribed order of preference, which differs by nationality — a rule that is mechanical but unforgiving. Instruments are identified by their international securities identification number, drawn from reference data rather than from the firm’s own catalogue.

The dependency on external reference data is the structural weakness of most implementations. A transaction executed on the day an instrument’s reference data changes, or before it appears at all, will not report cleanly, and no amount of internal data quality prevents it.

Where reports fail

• Instrument identification absent, stale, or drawn from an internal code rather than reference data.
• Entity identifiers lapsed, or missing for a client, which blocks the transaction rather than just the report.
• Natural person identifiers built in the wrong order of preference for the nationality concerned.
• Timestamps outside the required granularity, or inconsistent with clock synchronisation requirements.
• Conditional fields left empty when the condition that requires them is met — short selling indicators are the classic case.
• Chain misallocation, producing duplicates or gaps rather than malformed reports.

Note also that the framework is under revision: Regulation (EU) 2024/791 amends the transaction reporting regime, with transitional arrangements for some provisions. Build against the instrument in force for the transaction date rather than against a single fixed reading.

The United Kingdom position

The United Kingdom operates an onshored version of the same regime, supervised by its own authority and capable of diverging. A firm reporting on both sides of the Channel runs two obligations from one execution flow — the same transactions, two perimeters, two sets of reference data and two submission routes. Treat them as two implementations sharing a source, not as one implementation with a flag.

REGREP is an independent software provider. This record explains a reporting framework in plain language and is not legal, tax or regulatory advice. Confirm scope, thresholds and submission dates with your competent authority before you file.