Interest on interest - service tax

When we pay Service tax, S T Challan doesnt differentiate in Tax and Interest figure as in case of TDs payment. So whatever is the interest amount and service tax amount is all total which we require to pay on the payment day and if any balance remains will be treated as unpaid liability and interest has to be paid on in and there is nothing like interest on interest so it would be safer if we pay interest at the given rate because paying the interest on interest looks better than not paying interest at all and postponing the interest amount with the intent that interest can not be charged on interest.

As in your case your Service tax  liability due on 5th aug is Rs 30529/- and you are paying it on 5th Sept so interest for 31 days would be 467 @ 18% p a calculated day basis. (due date is 6th for e-payment) so the total would be 30966/- and you paid Rs 30529 on 5th sept so the balance payable would be 467 plus interest till the date of payment.

I think it should be Rs. 466 (i.e. 30,529X31days*X18%/365)

*31 days=== {6-sep-12 --5aug-12}+1