1. Without prejudice to Article 89, credit institutions and any parent undertaking and its subsidiaries shall implement the IRB Approach for all exposures.
Subject to the approval of the competent authorities, implementation may be carried out sequentially across the different exposure classes, referred to in Article 86, within the same business unit, across different business units in the same group or for the use of own estimates of LGDs or conversion factors for the calculation of risk weights for exposures to corporates, institutions, and central governments and central banks.
In the case of the retail exposure class referred to in Article 86, implementation may be carried out sequentially across the categories of exposures to which the different correlations in Annex VII, Part 1, points 10 to 13 correspond.
2. Implementation as referred to in paragraph 1 shall be carried out within a reasonable period of time to be agreed with the competent authorities. The implementation shall be
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