Non payment of ser tax, ag non receipt of payment from cust.

Dear Sir,

We have provided Services before Mar 2011, and paid service tax on payment basis, but payment from sum customers not received hence service tax also not paid to dept. by us on that invoices which are pending. 

Accounts dept has written off the pending balances. but  service tax liability is showing balance in our books of accounts, 

Can we write off the service tax payble amount, on which amount will not receive and written off. 

kindly suggest me.

Thanks