Vat registration delay

Suppose I am doing business from last 3 years an it is not crossed the T.O limit of vat registration of Rs.5 lacs. But in the 2010-11 I have notices that my sales cross the 5 lcas i.e total 10 lacs sale. Now I am plan to go for registration. So what impact will come on me while geting registration.

1) I am liable for pay tax for the above Rs.5 lacs (not collected from the party) with Interest?

2) If payable then shell I get any administrative Relief the from the Dept? (what is procedure for relief)

3) any good sugestion from you?

PLEASE ADVICE WHAT I WILL DO?

HELP ME URGENT

regards

mahendra