(20)To ensure legal certainty and consistency with Directive 2009/65/EC, for UCITS constituted after the date of entry into application of this Regulation, this Regulation should apply from 16 April 2026. Compliance with this Regulation would also require changes to the fund documentation and an update of the existing processes and technical infrastructure of UCITS and their management companies to support the activation of the selected liquidity management tools. It is therefore necessary to provide for a transitional period of one year for UCITS constituted before the date of application of this Regulation to enable those UCITS to adapt to the new regime. However, those UCITS should still have the possibility to choose to be subject to this Regulation from its date of application, i.e. from 16 April 2026.