23. Trade receivables - €11,533 million

Millions of euro     
 at Dec. 31, 2013 at Dec. 31, 2012 restated Change 
Customers:         
- sale and transport of electricity  8,738  8,838  (100)  -1.1% 
- distribution and sale of natural gas  1,524  1,570  (46)  -2.9% 
- other activities  1,200  1,243  (43)  -3.5% 
Total  11,462  11,651  (189)  -1.6% 
Trade receivables due from associates  34  29  17.2% 
Receivables for contract work in progress  37  39  (2)  -5.1% 
TOTAL  11,533  11,719  (186)  -1.6% 

Trade receivables from customers are recognized net of allowances for doubtful accounts, which totaled €1,482 million, at the end of the year, as compared with an opening balance of €1,421 million. The table below shows the changes in these allowances.

Millions of euro  
Total at January 1, 2012  1,661 
Accruals  588 
Utilization  (802) 
Other changes  (26) 
Total at December 31, 2012 restated  1,421 
Accruals  654 
Utilization  (546) 
Other changes  (47) 
Total at December 31, 2013  1,482 

Trade receivables that had not been written down at December 31, 2013 break down by maturity as follows:

Millions of euro  
Not past due  7,600 
Past due:   
- from 0 to 6 months  1,890 
- from 6 to 12 months  438 
- from 12 to 24 months  740 
- more than 24 months  865 
Total at December 31, 2013  11,533 

In a number of residual cases with no material impact on the financial statements, trade receivables have been netted against trade payables where permitted under contractual and statutory provisions.