The Financial Conduct Authority (FCA) has published final rules in Policy Statement PS25/17 implementing a package of UK market-structure and transparency changes consulted on in CP25/20. The package removes the Systematic Internaliser (SI) regime for bonds, derivatives, structured finance products and emission allowances, lifts restrictions on matched principal trading by multilateral trading facility (MTF) operators and on co-location of organised trading facilities (OTFs) and SIs within the same legal entity, and reforms the equity reference price waiver (RPW) to allow trading venues to source reference prices from a broader set of venues. The FCA is maintaining the SI regime in equities by updating Handbook references to an “equity systematic internaliser” and confirming that statutory opt-in is only available for equity SIs. It will end-date SI register entries for bonds and derivatives, meaning firms will not need to notify the FCA to de-register. For MTF matched principal trading, firms will need the appropriate dealing-as-principal permission and must comply with existing conduct, conflicts and prudential requirements, including a permanent minimum capital requirement of GBP 750,000 under MIFIDPRU when trading on a matched principal basis. On RPW, the FCA implemented the broader sourcing change but did not proceed with its separate proposal to allow mid-price dark orders on lit order books, indicating it will gather more information and consult on any related post-trade transparency changes as part of future equity transparency work. Commencement is split across dates set out in the made instruments, with core SI regime changes taking effect on 1 December 2025 and further Handbook and technical standards changes for equity pre-trade transparency waivers taking effect on 30 March 2026, alongside transitional provisions running to 30 June 2026 for venues relying on existing waivers while updating rulebooks. The FCA also plans to consult on equity markets in the first half of 2026.