What is gst on transport business

Dear Members,

Can anyone explain what is the GST on Transportation Business. I am having 2 Trucks (40' Trailers) for Conatiner movement and running the business from Last 2 years as a Propreitor with an annual revenue less than 20 Lacs. I use to submit a normal trasnport bill to the companies before, so how should i raise the transport bill now, with GST ?  do i need to register for GST as my turnover is less than 20 lacs.. if GST than how much % i need to charge the companies for transportation.

Please suggest.

Thanks