TN VAT

I am doing a business and i am under the 0.5% tax scheme. i know i am eligible for this only my turnover is up to 50 lakhs. i like to know whether i can switch over to regular tax scheme of claiming input tax and paying vat tax according to the tax rates of purschase and sales, once my turnover crosses 50 lakhs. is there any provisions in the act to automatically switchover, or i need to inform the official concerned.   if any body knows the solution to the above pls. post

viswanathan