relief on impairment loss under VAT.

Mick is a value added tax registered trader who prepares quarterly value added returns to 31 March, 31 July, 31 September and 31 December. Mick’s accounts are prepared annually to 30 September. Mick made a supply of goods amounting to £6000 on September 22 2014 with a due date of payment of 10 October 2014. The customer has defaulted on the payment and Mick has written the debt off in his accounts. He does not use the cash accounting scheme. In which quarterly VAT return may relief for the impaired debt be claimed?