(6)The depositary should take all necessary steps to ensure that appropriate valuation policies and procedures for the assets of the UCITS are effectively implemented, through the performance of sample checks or by comparing the consistency of the change in the net asset value (NAV) calculation over time with that of a benchmark. When setting up its procedures, the depositary should have a clear understanding of the valuation methodologies used by the UCITS to value the UCITS' assets. The frequency of such checks should be consistent with the frequency of the UCITS' asset valuation.