Cst sales and payment default

Hi,

CST sales @ 2% (with C form ) was entered. However sales party defaulted in payment and ran away with the goods. Hence no payment or C-form received. So in this case can we show as sales reversal (bad debts) and claim CST input credit of CST already paid on accrual basis? If reversal possible, then any time limit for the same i.e within 6 months of bill date or any other condition?

If reversal not possible , then will the differential tax amount (CST rate - VAT rate) be payable?