89 AGL Energy Limited Annual Report 2012 2012  $m 2011  $m Note 13 – Trade and other receivables (current) Trade receivables 697.7  551.9  Allowance for doubtful debts (75.3) (64.6) 622.4  487.3  Unbilled revenue 833.5  694.6  Amounts owing by associates –  4.1  Amounts owing by jointly controlled entities 51.7  54.8  Amounts owing by joint venture operations 0.8  –  Other receivables 23.0  31.3  1,531.4  1,272.1  Allowance for doubtful debts Movements in the allowance for doubtful debts are detailed below: Balance at beginning of financial year 64.6  63.5  Impairment losses recognised on receivables 66.9  62.6  Amounts written off as uncollectible (56.2) (61.5) Balance at end of financial year 75.3  64.6 2012 2011 Total $m  Allowance $m  Total $m  Allowance $m  Not past due 462.6  (5.6) 360.7  (6.7) Past due 31–60 days 51.2  (7.1) 49.8  (3.3) Past due 61–90 days 22.8  (6.7) 20.8  (3.5) Past 90 days 161.1  (55.9) 120.6  (51.1) 697.7  (75.3) 551.9  (64.6) The ageing of trade receivables at the reporting date is detailed below: The consolidated entity’s policy requires customers to pay in accordance within agreed payment terms. Depending on the customer  segment, settlement terms are generally less than 30 days from date of invoice. An allowance for doubtful debts is recognised when  there is objective evidence that a trade receivable is impaired. Financial difficulties of the debtor, default payments or debts overdue  are considered objective evidence of impairment. An impairment loss for doubtful debts of $66.9 million (2011: $62.6 million) has been  recognised in the year and has been included in other expenses in Note 7. At the end of the reporting period, trade receivables with a carrying amount of $166.8 million (2011: $133.3 million) were past due but not  considered impaired. These trade receivables relate to customers for whom there has not been a significant change in credit quality and the  amounts are considered recoverable.  Other balances within trade and other receivables are neither impaired nor past due. It is expected that these other balances will be  received when due.  Unbilled gas and electricity revenue is not collectible until such time as customers’ meters are read and bills rendered.  For terms and conditions relating to amounts owing by associates and jointly controlled entities, refer to Note 50.  Due to the short-term nature of these receivables, their carrying amount is assumed to approximate their fair value. The maximum  exposure to credit risk at the reporting date is the carrying amount of each class of receivables. Collateral is not held as security.  Unbilled revenue  Amounts owing by associates and jointly controlled entities  Fair value and credit risk 