The final deadline to register qualifying groups with a year end of 31 December 2024 liable for Pillar Two reporting is Monday 30 June. 

This is a one-off online registration with HMRC and it will not be necessary to re-register in future years once within the tax regime, but it is mandatory, even if companies do not think they will have to pay any tax under the rule change.

The June date is for initial registration, not payment of the first tax instalment, which is not due until 30 June 2026 at the earliest depending on accounting years.