Bad debts provision of service tax invoice

Hi,

I have raised a invoice 2 years back against that invoice i have'nt receive collection till today now management has decieded to write off the same. So far i have not paid the service tax portion on that invoice.Now am i liable to pay service tax or not.Can i write off the total invoice amt.For that do i need to submit any correspondence to the dept.

Regards

S.Naresh