There will not be any harassment, if you declare everything, on your own. They will ask you to pay, the back-log, only. Since, it is Voluntarily Disclosure, they may waive the penalty. Even then, if they insist, you will have to pay. Better, you seek an appointment with Director General of Service Tax along with, your Auditor, and appraise him, clearly. You are in which place. If known, I may be able suggest, a reliable person to represent you.