(17)Article 180(2), point (c), of Regulation (EU) No 575/2013 requires that, for retail exposures, institutions regard internal data for assigning exposures to grades or pools as the primary source of information for estimating loss characteristics. However, where the institution calculating K IRB was not involved in, or did not conclude, the original agreement that gave rise to the qualifying securitised exposures, and is not the servicer of those exposures, the internal data of the institution calculating K IRB should not be considered the best available data for the comparison with the qualifying securitised exposures to quantify risk parameters. Accordingly, external data related to the qualifying securitised exposures should instead be considered as the primary source of information for those purposes.