What if service tax will liable on 11th month onward

Indiatrainer (Head) (61 Points)

04 February 2014  
Every month my business was less than 50K, so I thought of not charging ST from my clients, as the projected business was less than 10L thus in exempted limit. Now suddenly on 11th month and onward I am hoping for big business, and would easily cross 10 L limit. If I charge ST now onward, will there be any issue? (as I said I have never charged ST as of now from my clients). Will the department ask about ST for all the previous businesses in the financial year? So what should I do ?