Receivables impairment: change in technique, revision of a provision or error? Classification and disclosure

Laboratoires Pelvanne SA (fictitious entity) is preparing its 20X5 statements (20X4 comparative). The CFO proposes three treatments: (a) the loss allowance on receivables, so far computed with an ageing matrix, is now computed with a roll-rate model made possible by the new collection software; it goes from 268,000 to 312,000; he wants to present this as a change in policy restated, "so as not to penalise 20X5"; (b) the provision for product returns goes from 150,000 to 118,000 thanks to the more detailed 20X5 return statistics; (c) a 26,000 credit note granted to a customer was posted twice in December 20X3; the duplicate appeared in the customer's statement received in January 20X4, before the 20X3 statements were approved. Draft 20X5 profit before (a) and (b): 1,250,000.