(12)Most Union corporates, however, do not seek external credit ratings. To avoid a disruptive impact on bank lending to unrated corporates and to provide enough time to establish public or private initiatives aiming to increase the coverage of external credit ratings, it is necessary to provide for a transitional period. During that transitional period, institutions using the IRB Approach should be able to apply a favourable treatment when calculating their output floor for investment grade exposures to unrated corporates, whilst initiatives to foster a widespread use of credit ratings should be established. Any extension of the transitional period should be substantiated and limited to four years at most.