Excise duty payable

Our company is engaged in manufacturing of auto parts. In the FY 2012-13 we have exported goods worth Rs 50 lakhs to UK based firm under UT1 Bond (Without payment of duty). After some time span our company realized that UK based firm becomes bankrupt and the dues recoverable from them became doubtful. Our management has decided to make provision for bad and doubtful debts in Balance sheet for FY 2012-13. My question is that should we need to provide for excise duty payable on the export sale becomes doubtful? If yes, what will be nature of liability? contingent or non-contingent Please help ASAP