14. Customer and other receivables

2014
£m
2013
£m
Directory customer receivables806.4726.6
Less: allowance for doubtful debts(124.2)(125.4)
682.2601.2
Other trade receivables21.621.2
Less: allowance for doubtful debts(0.2)(0.2)
703.6622.2
Amounts due from associated undertakings1.00.8
Other debtors9.48.3
Prepayments94.086.8
808.0718.1

No interest is charged on Directory customer receivables if the statement balance is paid in full; otherwise balances bear interest at a variable annual percentage rate of 25.99% (2013: 25.99%).

Expected irrecoverable amounts on overdue balances are provided for based on past default experience. Receivables which are impaired, other than by age or default, are separately identified and provided for as necessary.

The credit quality of customer receivables that are neither past due nor impaired can be assessed by reference to the historical default rate for the preceding 365 days of approximately 1% (2013: 1%), although default rates over shorter periods may show significant variations.

Other debtors and prepayments do not include impaired assets. The maximum exposure to credit risk at the reporting date is the carrying value of each class of asset. The Group does not hold any collateral over these balances.

Ageing of customer and other trade receivables:

2014
£m
2013
£m
Not past due687.2609.7
0 – 30 days past due46.440.0
30 – 60 days past due10.49.2
60 – 90 days past due3.83.5
90 – 120 days past due2.82.2
Over 120 days past due55.663.9
Otherwise impaired21.819.3
Total customer and other trade receivables828.0747.8

Movement in the allowance for doubtful debts:

2014
£m
2013
£m
Opening position125.6113.7
Charged to the income statement29.028.3
Written off as uncollectible(25.6)(11.7)
Recovered during the year(4.6)(4.7)
Closing position124.4125.6