MIFIR EU & UK

An ARM (Approved Reporting Mechanism) is a firm authorised to submit transaction reports to national competent authorities on behalf of investment firms under MiFIR Article 26. ARMs validate, format and route reports to the correct regulator. In the EU, ARMs are authorised under MiFIR; in the UK, they are authorised by the FCA as data reporting services providers. Using an ARM does not transfer the investment firm's legal responsibility for complete and accurate reporting.

Investment firms that execute transactions in reportable financial instruments must report those transactions to their national competent authority. The obligation sits with the executing firm, whether trading for clients or on own account. Trading venues must also report transactions executed through their systems by firms not subject to MiFIR. Credit institutions performing investment services are in scope. UK investment firms have the equivalent obligation under UK MiFIR, reporting to the FCA.

Transaction reports must be submitted as quickly as possible and no later than the close of the working day following the trade (T+1). Reports are made to the firm's national competent authority — directly, through an ARM, or via the trading venue where applicable. Late reporting, over-reporting and under-reporting are all treated as breaches of Article 26.

A MiFIR transaction report contains 65 fields, defined in RTS 22. They cover the buyer, seller and decision-makers (including natural-person identifiers), the instrument (ISIN), price, quantity, venue, timestamps to the required granularity, and flags such as short-selling and waiver indicators. Identifier accuracy — LEIs for legal entities and national identifiers for natural persons — is one of the most common sources of rejection and regulator queries.

Reportable instruments are those admitted to trading or traded on an EU trading venue (or for which admission has been requested), plus instruments whose underlying is such an instrument or an index or basket of such instruments — the "TOTV" and "uTOTV" tests in Article 26(2). Firms typically check reportability against ESMA's FIRDS reference database, or FCA FIRDS for UK MiFIR, on the relevant trade date.

MiFIR transaction reporting is a market-abuse surveillance regime; EMIR is a systemic-risk regime for derivatives. MiFIR reports go to the regulator (via an ARM or directly) in a 65-field format covering all reportable instrument classes, single-sided per executing firm. EMIR reports go to a trade repository, cover derivatives only, are two-sided with reconciliation, and carry 203/204 fields. Many derivative trades are reportable under both regimes simultaneously, with different field content and deadlines.

Submission can be delegated — most firms report through an ARM, and some rely on their broker or a service provider to prepare and route reports — but legal responsibility cannot. The executing investment firm remains accountable for the accuracy, completeness and timeliness of its transaction reports, and is expected to reconcile its front-office records against samples of the data the regulator actually received, as set out in RTS 22 Article 15.

UK MiFIR is the onshored version of MiFIR that has applied to UK investment firms since the end of the Brexit transition period on 31 December 2020. The core Article 26 obligation and 65-field RTS 22 format are substantially the same, but reports go to the FCA, reportability is checked against FCA FIRDS rather than ESMA FIRDS, and the two rulebooks and validation rules can diverge over time. Firms in scope of both regimes must report separately to each.