GST registration is mandatory for all enterprises involved in the supply of goods or services or both & the annual turnover exceeding Rs.10 lakhs a year in north-eastern and hill states, while the limit is Rs.20 lakhs for rest of India. Unregistered persons will not be allowed to collect GST from customers or claim ITC & if they do so, they will be penalized. Apart from this criterion of turnover, the GST Act provides various other categories where registration is mandatorily required like supply under RCM, e-commerce aggregator, etc. irrespective of their turnover.
It should be noted that GST registration must be applied within 30 days from the date becoming liable for registration. The penalty for non-payment & short payment of tax is prescribed at the rate of 10% of the tax amount subject to a maximum of Rs. 10,000. If there is deliberate evasion of tax then the penalty can be 100 % of the tax amount.