GST registration is mandatory for businesses whose aggregate turnover in a financial year exceeds Rs 40 lakhs (Rs 20 lakhs for special category states). However, certain businesses must register regardless of their turnover. This includes interstate suppliers, e-commerce operators, and businesses liable to pay tax under the reverse charge mechanism.
To apply, you need essential documents like PAN, Aadhaar, business address proof, and bank account details. The process is entirely online via the GST portal, and understanding the nuances can help avoid rejection and subsequent delays.