(2)Pursuant to Article 258 of Regulation (EU) No 575/2013, institutions are to apply SEC-IRBA where they are able to calculate ‘K IRB ’ in accordance with Article 255, (2) to (5) of that Regulation. Where the conditions of that Article are met, institutions may calculate K IRB in relation to the securitised exposures in accordance with the provisions set out in Part Three, Title II, Chapter 3, of Regulation (EU) No 575/2013 for the calculation of capital requirements for purchased receivables. For those purposes, retail exposures are to be treated as purchased retail receivables and non-retail exposures as purchased corporate receivables. Due to the particular nature of the structure of securitisations and the exposures underlying those securitisations, it is necessary to adopt regulatory technical standards that further specify the conditions under which institutions can calculate K IRB for pools of securitised exposures. The provisions set out in Part Three, Title II, Chapter 3, of Regulation (EU) No 575/2013 should, therefore, be tailored as much as necessary to suit the determination of the risk-weighted exposure amounts of the securitised exposures. The application of some other of those IRB provisions in the context of securitisation is, however, not appropriate, either because such rules are not relevant, because they do not lead to prudent outcomes, or because they would be too burdensome for institutions in the context of securitisation. Therefore, for all such cases, alternative rules should be laid down that are appropriate in the context of securitisation.