Notes to the consolidated annual financial statements l Note 14   Rm 2016    2015    14. Trade and other receivables                 Trade receivables  9 644     8 017        Prepayments  1 463     1 620        Accrued income  1 937     1 915        Value-added tax  39     40        Derivative financial assets  73     124        Other  873     606           14 029     12 322        Timing                 Non-current  754     763        Current  13 275     11 559           14 029     12 322        Doubtful receivable allowance included above:                 The Group’s trade receivables are stated after allowances for doubtful receivables based on management’s assessment of creditworthiness, an analysis of which is as follows:                 1 April  (828)    (319)          Foreign currency translation differences  3     (19)          Charged to profit or loss  (312)    (534)          Utilised  34     44        31 March  (1 103)    (828)       Trade receivables are carried at cost which normally approximates fair value due to short-term maturity. Generally no interest is charged on trade receivables.                 Included within derivative financial assets:                 At fair value through profit or loss, classified as held for trading:                 Fair value hedges:                    Foreign exchange forward contracts  62     100           Firm commitment asset – fair value hedge  11     24           73     124       The fair value of foreign exchange forward contracts is determined with reference to quoted market prices for similar instruments, being the mid forward rates as at the reporting date. During the prior year the Group designated certain forward exchange contracts as fair value hedges to hedge its exposure to variability in the fair value that is attributable to changes in foreign exchange rates.