1. A CCP shall regularly review the models and parameters adopted to calculate its margin requirements, default fund contributions, collateral requirements and other risk control mechanisms. It shall subject the models to rigorous and frequent stress tests to assess their resilience in extreme but plausible market conditions and shall perform back tests to assess the reliability of the methodology adopted. The CCP shall obtain independent validation, shall inform its competent authority and ESMA of the results of the tests performed and shall obtain their validation in accordance with paragraphs 1a to 1e before adopting any significant change to the models and parameters.

Where a CCP intends to adopt a change to a model or parameter referred to in the first subparagraph, it shall do one of the following:

(a) where the CCP considers that the intended change is significant pursuant to paragraph 1i, it shall apply for validation of the change in accordance with the procedure laid down in this Article;

(b) where the CCP considers that the intended change is not significant pursuant to paragraph 1i of this Article, it shall apply for validation of the change in accordance with the procedure laid down in Article 49a.

1a. All changes to models and parameters not assessed under Article 49a shall be assessed in accordance with the procedure laid down in this Article.