Service tax bill entry

Please specify the mode of Payment, Cash / Bank /  Due to the party

its due to the party. please specify accounting heads for journal entry.

Computer Expenses A/c Dr. (Final Amount of the bill to be taken here)

Party A/c Cr, (Final Amount of the bill to be taken here)

1. Was your concern have the Service tax registretion ?

If your concern have service tax liability you can claim this amount as input other wise, showing the entire amount as expenditure is good enough.