Sir,
You have stated that you had taken credit of service tax paid on input service and had not utilized since 2006. but you have not mentioned the date on which the Auditor asked you to reverse the credit. if that date falls in the year 2012, then the demand is clearly time barred. Since the credit taken by you would have reflected in your ST-3 return you cannot be accused by the department of suppression of fact etc., under Section 73 of finance Act, 1994.
Rule 14 of Cenvat Credit Rules, 2004 states that-
14. Recovery of CENVAT credit wrongly taken or erroneously refunded.-
Where the CENVAT credit has been taken and utilised wrongly or has been erroneously refunded, the same along with interest shall be recovered from the manufacturer or the provider of the output service and the provisions of sections 11A and 11AA of the Excise Act or sections 73 and 75 of the Finance Act, shall apply mutatis mutandis for effecting such recoveries.
Interest is payable under Section 11 AA. The rate of interest is 18% per annum vide Notification No. 5/2011-CE (N.T) dated 1.3.2011.
A reading of the above mentioned provision reveals that only when cenvat credit is wrongly taken and utilised then you have to reverse the wrongly taken and utilised credit along with interest. The words "taken and utilised" was inserted in rule 14 of Cenvat Credit Rules, 2004 vide Notification No. 18/2012 CE(NT) dated 17-3-2012. If the department asked you to reverse the credit on or after 17.3.2012 you need not pay any interest since you had not utilised the credit for payment of duty or service tax.
I have not come across any provision under Finance Act, 1994 or Service Tax Rules, 1994 for payment of 1% interest penalty. Only under Rule 8 (3 A) of Central Excise rules, 2002 if the assessee fails to pay the duty declared as payable by him in the return within a period of one month from the due date, then the assessee is liable to pay the penalty at the rate of one per cent on such amount of the duty not paid, for each month or part thereof calculated from the due date, for the period during which such failure continues . The period of one month is calculated from 5th or 6th of the month to 5th or 6th of the next month.