The FCA has finalised changes to the UK's transactionreporting regime following a consultation last year. The regulator estimatesthat the industry currently spends £493 million annually on transactionreporting and expects the reforms to save more than £100 million a year.These are arguably the most significant changes to UK MiFIRtransaction reporting since MiFID II came into force in 2018.London's trading industry is coming home!That is welcome news. However, anyone who has been throughEMIR Refit will know that simplification does not necessarily mean less work.Changes to reporting schemas, newvalidation rules and months of regression testing can quickly offset someof the expected savings. Much of the reduction in trade repository chargescould be absorbed by the personnel time required to adjust to the newspecifications.What Is Changing?The main changes fall into three areas: what firms mustreport, which instruments fall within scope and how far back firms must correctreporting errors.The number of reportable fields will fall from 65 to 52.Trading venues will also no longer need to provide 11 instrument reference datafields.The scope of reporting will become narrower, with aroundseven million instruments that are tradable only on EU venues removed from UKreporting requirements.Another significant change concerns FX derivatives, whichwill be removed from MiFIR transaction reporting altogether. The FCA considersUK EMIR a more appropriate reporting framework for this data. Thechange is expected to reduce costs for more than 400 UK firms whileremoving duplication.The maximum period for correcting historical reportingerrors will also fall from five years to three. In addition, the exemption forcorporate events will be widened, although IPOs, secondary offerings, placingsand debt issuance will remain reportable.For retail FX and CFD brokers, the removal of FX derivativesfrom MiFIR reporting is arguably the most important change. Reporting the sametransaction under two separate regimes, using different formats and sending thedata to different destinations, has long been one of the less defensibleaspects of the UK reporting framework.Why Does FIRDS Becoming the Golden Source Matter?The FCA has confirmed that its Financial InstrumentsReference Data System will become thedefinitive source for determining whether an instrument is reportable. A clearseven-day cut-off after execution will also apply.In practice, this should remove the need for firms to keepchecking whether an instrument has entered FIRDS and become reportable after atransaction has taken place.However, placing greater reliance on FIRDS also increasesthe importance of data governance. Firms will need to understand where theirreference data comes from, how frequently it is refreshed and who isresponsible for managing it internally.The FCA is also addressing reporting requirements forderivatives on indices, where determining whether a transaction is reportablecan be difficult. Firms will be allowed to voluntarily over-report thesetransactions.Formany brokers, reporting all transactions in this category may prove simplerand less expensive than developing systems to determine which ones fall outsidethe reporting requirements.Will Conditional Single-Sided Reporting Deliver RealRelief?PS26/15 introduces a new Conditional Single-Sided Reportingframework. Its purpose is to allow more firms to rely on reporting arrangementswith counterparties instead of reporting the same transaction twice.Thedirection is welcome, but there are reasons to question how much relief theframework will deliver in practice. Several buy-side respondents told the FCAthat they were sceptical about its potential benefits.Delegating reporting responsibilities to a counterparty mayappear straightforward. However, it requires accurate data sharing, clearlydefined responsibilities and appropriate contractual arrangements. Withoutthese elements, firms risk replacing one operational burden with another.Ultimately, the framework's value will depend on theconditions attached to it and how easily firms can meet them.When Do the Changes Take Effect?The new reporting regime will become fully effective on 3April 2028. However, firms should pay attention to three dates in theimplementation timeline.From 3 August 2026, the FCA is adopting a flexiblesupervisory approach across a defined list of areas. Firms will not faceenforcement action for adopting several of the changes early. The shorterthree-year back-reporting period also applies from this date.In October 2026, the FCA is expected to publish a draftschema, validation rules and updated guidance. Together, these documents willform the Transaction Reporting User Pack.Full implementation will follow on 3 April 2028.The October 2026 publication is particularly important.Until firms have access to the revised schema and validation rules, they canassess the scope of system changes but cannot begin building against the finaltechnical specifications.Why Does This Matter Beyond MiFIR?The reforms are also part of a broader effort to simplifyregulatory reporting in the UK.The FCA and the Bank of England have established a jointTransaction and Post-trade Reporting Industry Harmonisation Taskforce. Itsobjective is to develop a single reporting framework covering UK MiFIR, UK EMIRand UK SFTR.The underlying principle is straightforward: firms shouldonly have to report data once.This could eventually address some of the overlap betweenthe three reporting regimes. Firms should therefore expect furtherconsultations as regulators explore ways to harmonise their requirements.How Should Firms Prepare?Although the FCA does not require firms to take immediateaction, the scale of the changes and the time needed to implement them make itunwise to wait until 2028.Reporting teams and their external service providers shouldalready be reviewing their existing arrangements.In particular, firms should:Review reporting logic against the revised scope, with particular attention to FX derivatives and instruments traded exclusively on EU venues.Assess data governance arrangements and reference data sources ahead of FIRDS becoming the definitive source for determining reportability.Check whether correction and back-reporting procedures reflect the new three-year limit, which already applies.Monitor the publication of the October 2026 schema and validation rules, and allocate sufficient time and resources for the necessary system changes.PS26/15 represents a step towards a leaner UK transactionreporting regime. The expected reduction in reporting costs is welcome,particularly for firms that have had to manage overlapping requirements acrossdifferent regulatory frameworks.However, the savings will not come automatically. Firmsstill face the work of updating systems, reviewing data processes and ensuringthat their reporting arrangements meet the revised requirements.Those that use the next 18 months to review their data, mapreporting flows and prepare for the technical changes should be in a betterposition to benefit from the reforms. Those that wait until 2028 risk turning asimplification exercise into another last-minute compliance project.This article was written by Quinn Perrott at www.financemagnates.com.