Aggregate Turnover

Yes you are required to register in GST regime if your turnover is 20 lakh

CASE 1 :If your turnover is 20 lakh means you are selling goods worth Rs 20 lakh which is not,so you are not required to register

CASE 2 : you need to register as your turnover is 21 lakh

Turnover is Consider based on Supply of Goods, further we suggest that in case no.1 If you purchase 30 Lacs worth of Purchase and Paying GST on that, and whatever your Sales of 15 Lacs you are not collecting GST if you are Unregister, further If you take GST registration compulsory on 20 Lacs Turnover now your Case 1 Purchase 30 Lacs GST Credit will not be allowed for your balance Stock of Rs. 30 Lacs - 15 Lacs = 15 Lacs laying with you. As us suggest that it's better to take GST registration right from the beginning and take entire credit of GST which you paid on Purchases.