NOTES TO THE CONSOLIDATED FINANCIAL  STATEMENTS  (RMB AND US$ AMOUNTS EXPRESSED IN THOUSANDS, EXCEPT PER SHARE DATA)  19.  Trade and bills receivables (i)  As of December 31, 2013, bills receivable includes bills receivable from joint venture and other related parties  amounted Rmb 126,027 (US$20,592) (2012: Rmb 99,632) and Rmb 6,800 (US$1,111) (2012: Rmb 21,070), respectively. Trade receivables (net) are non-interest bearing and are generally on 60 days’ term. They are recognized at their original  invoice amounts which represent their fair values on initial recognition. As of December 31, 2012 and 2013, outstanding bills receivables discounted with banks for which the Group retained a  recourse obligation totaled Rmb 828,974 and Rmb 1,243,440 (US$203,173) respectively. As of December 31, 2012 and 2013, outstanding bills receivables endorsed to suppliers with recourse obligation were  Rmb 567,112 and Rmb 1,043,213 (US$170,457) respectively. An analysis of the allowance for doubtful accounts is as follows: The Group’s historical experience in the collection of trade receivables falls within the recorded allowances. Due to  this factor, management believes that no additional credit risks beyond the amount provided for collection losses are  inherent in the Group’s trade receivables. As of December 31, 2012 and 2013, gross trade receivables due from a major customer, Dongfeng Automobile  Company and its affiliates (the “Dongfeng companies”) were Rmb 145,351 and Rmb 279,831 (US$45,723), respectively.  See Note 31 for further discussion of customer concentration risk. China Yuchai International Limited | Annual Report 2013 98 31.12.2012 31.12.2013 31.12.2013 Rmb’000 Rmb’000 US$’000 Trade receivables (net) 395,025 411,782 67,283 Bills receivable  (i) 6,196,711 7,026,166 1,148,048 6,591,736 7,437,948 1,215,331 31.12.2012 31.12.2013 31.12.2013 Rmb’000 Rmb’000 US$’000 At January 1 59,177 43,664 7,135 Credit to consolidated statement of profit or loss (15,184) (12,669) (2,070) Written off (334) (2,454) (401) Translation differences 5 (8) (2) December 31 43,664 28,533 4,662 Neither  past due Past due but not impaired Total nor  impaired 0 – 90 days 91-180  days 181-365  days >365 days Rmb’000 Rmb’000 Rmb’000 Rmb’000 Rmb’000 Rmb’000 At 31.12.2013 7,437,948 7,279,974 121,648 12,948 23,039 339 At 31.12.2012 6,591,736 6,417,854 120,507 25,962 9,310 18,103