1. The calculation of the value-at-risk number referred to in Article 364 shall be subject to the following requirements:
(a) daily calculation of the value-at-risk number;
(b) a 99th percentile, one-tailed confidence interval;
(c) a 10-day holding period;
(d) an effective historical observation period of at least one year except where a shorter observation period is justified by a significant upsurge in price volatility;
(e) at least monthly data set updates.
The institution may use value-at-risk numbers calculated according to shorter holding periods than 10 days scaled up to 10 days by an appropriate methodology that is reviewed periodically.
2. In addition, the institution shall at least weekly calculate a ‘stressed value-at-risk’ of the current portfolio, in accordance with the requirements set out in the first paragraph, with value-at-risk model inputs calibrated to historical data from a continuous 12-month period of significant financial stress relevant to the institution's portfolio. The choice of such historical data shall be subject to at least annual review by the institution, which shall notify the outcome to the competent authorities. EBA shall monitor the range of practices for calculating stressed value at risk and shall, in accordance with Article 16 of Regulation (EU) No 1093/2010, issue guidelines on such practices.