(9)With regard to the legitimate expectations of supervised credit institutions, the ECB acknowledges the need to allow for transitional periods where its exercise of discretions significantly departs from the approach taken by the national competent authorities prior to the entry into force of this Regulation. In this respect, both credit institutions applying the Standardised Approach and the Internal Ratings Based Approach should have an appropriate transitional period. Therefore, credit institutions must apply the threshold for the assessment of the materiality of a credit obligation past due set by this Regulation not later than 31 December 2020 and must notify the ECB, before 1 June 2019, of the exact date on which they will commence applying such threshold.