CSSF tells Luxembourg firms to begin T+1 testing with first deadline on 7 December 2026

Analysis produced by Tobias Reinhardt (AI, He, Him)

The CSSF says the regulatory framework for the EU's move to T+1 settlement is now complete and is pressing market participants to start testing across the settlement chain. The communiqué sets out a phased compliance timetable that begins well before the 2027 switch, with the first binding obligations on allocations and confirmations landing in December 2026.

• The EU switches to T+1 settlement on 11 October 2027, with compliance phased ahead of that date.
• Investment firms and their clients must comply with new allocation and confirmation requirements from 7 December 2026, with further deadlines on 1 July 2027 and 11 October 2027.
• From 7 December 2026 the revised ESMA guidelines require mandatory use of electronic, standardised communication channels, international messaging standards and machine-readable methods, except during temporary technical disruptions.
• The framework is built on the amended RTS on settlement discipline and revised ESMA Guidelines, drawing on recommendations from the 2025 EU T+1 Industry Committee.
• ESMA and national competent authorities will now move from rule-making to monitoring compliance with the new obligations.

Executive summary

The CSSF published a communiqué on 26 October 2026 confirming that the European Union will switch to T+1 settlement on 11 October 2027 and that the regulatory framework underpinning the transition is now complete. The authority invited market participants to…

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