The discounting of the provision is to give as accurate an indication as possible of the PV of the future cost. Changing the rate might be a sensible response to eco omic changes. If so, that’s fine. As it says in the answer, “the audit team must fully understand the reasons for the reduction in the provision”. One reason is a re-estimation of the discount rate. An invalid reason would be changing it arbitrarily to boost profits (an example of creative accounting/fraud).