T+1 – Corporate Events Harmonised Implementation Guide

On July 23, 2026, the European Central Bank's Advisory Group on Market Infrastructures for Securities and Collateral (AMI-SeCo) published an updated version of its T+1 – Corporate Events Harmonised Implementation Guide.

The Guide explains how the shortened settlement cycle affects the sequencing of key corporate-action dates and details how market infrastructures and intermediaries—including CSDs, CCPs, and custodians—should process these events and communicate related instructions.

The updated version largely preserves the structure and operational framework of the March 2026 edition but introduces several targeted refinements.

Revised timelines for corporate-action processing. The Guide now recommends that payment dates for mandatory distributions and mandatory reorganizations occur one business day after the record date, upgrading this from a merely "preferred" practice to a firm recommendation. For elective corporate events, the recommended timing of the guaranteed participation date has changed: it should now fall at least one business day before both the buyer protection deadline and the market deadline. This replaces the previous recommendation of a one-business-day interval before the buyer protection deadline and a two-business-day interval before the market deadline. The Guide also clarifies that the last trading date applies only to mandatory reorganizations with options (CHOS events).

Updated market claims rules. The period during which CSDs, and where applicable CCPs, should identify and create market claims following the record date has been reduced from 20 business days to 10 business days. The Guide also revises the reverse market claim rules, limiting them to transactions executed on the ex-date rather than to transactions executed at any point after the ex-date. The use of "ex" and "cum" indicators for determining market claims has been removed. A new table has been introduced specifying the hold and release status of market claim instructions throughout the corporate-action lifecycle.

Expanded buyer protection provisions. The Guide substantially expands the operational rules governing buyer protection, introducing detailed lifecycle management provisions covering the interaction between buyer protection instructions and pending settlement transactions. New rules specify how the underlying settlement transaction should be handled when it is placed on hold, cancelled, or transformed following a corporate reorganization, or otherwise changes during processing. Additional operational events and corresponding processing rules have been added throughout the buyer protection process.

Implications for market participants. All participants involved in securities settlement and corporate-action processing—including CSDs, custodians, broker-dealers, institutional investors, and CCPs—should review the updated guidance and assess its impact on their T+1 implementation programs. Firms should verify that their operational processes, systems, and internal procedures reflect the revised recommendations on corporate-action timelines, the updated market claims practices, and the enhanced buyer protection lifecycle guidance. Firms should also review their settlement workflows and messaging arrangements, and coordinate with counterparties and market infrastructures, to ensure these refinements can be implemented consistently ahead of the EU's transition to T+1 settlement on October 11, 2027.