What is the threshold for registration in GST?

A person having business which has aggregate turnover of more than Rs. 20 lakhs calculated for a given PAN across the country would need to register under GST. There are some exceptions to this rule as mentioned in section 24 of the CGST Act, 2017. Aggregate turnover is defined in section 2(6) of the said Act.
For example, assume that a taxable person’s business is in many States on same PAN. All supplies are below Rs. 10 lakhs but collectively they are above Rs. 20 lakhs. He would be
required to register under GST.