18. Trade and other receivables

GroupCompany
2013
£000
2012
£000
2013
£000
2012
£000
Trade receivables13,11716,185
Less: provision for impairment of trade receivables(252)
Trade receivables — net13,11715,933
Amounts receivable from Group undertakings5261,398
Contingent consideration11,676
Other receivables1,040923
Other taxation81631160686
Prepayments and accrued income1,5531,1897389
28,20218,3561,8701,493
Due after more than one year: deferred consideration5,424
Due within one year22,77818,3561,8701,493

The maximum exposure to credit risk at the reporting date is the carrying value of each class of receivable mentioned above. The Group does not hold any collateral as security.

Amounts receivable from Group undertakings include amounts denominated in US dollars and include short-term loans on which interest is charged at rates linked to LIBOR.

As at 30 April 2013, trade receivables of £828,000 (2012: £2,148,000) were past due.

Contingent consideration arises on the disposal of King Systems and is stated at fair value.

The ageing of overdue receivables is as follows:

Group
2013
£000
2012
£000
Up to 3 months7851,650
3 to 6 months2268
Over 6 months41230
8282,148

The ageing of impaired receivables is as follows:

Group
2013
£000
2012
£000
Up to 3 months
3 to 6 months142
Over 6 months110
252

The credit quality of receivables that are neither past due nor impaired is considered to be good.

There are no receivables that would otherwise have been past due or impaired had their terms not been renegotiated (2012: £nil).

The carrying amount of the Group's trade and other receivables is denominated in the following currencies:

Group
2013
£000
2012
£000
Sterling13,33810,509
US dollars12,2096,324
Euro1,7501,523
Swiss franc905
28,20218,356

Movements on the Group provision for impairment of trade receivables are as follows:

Group
2013
£000
2012
£000
At 1 May25248
Provision for impairment of receivables200
Receivables written off in the period(174)(3)
Disposal of subsidiaries(85)
Exchange movement77
At 30 April252

Amounts are written off when there is no expectation of recovering additional cash. The other classes within trade and other receivables do not contain impaired assets.