What happens if I wont collect gst after registration?

An offender not paying tax or making short payments must pay a penalty of 10% of the tax amount due subject to a minimum of Rs. 10,000. Consider — in case tax has not been paid or a short payment is made, a minimum penalty of Rs 10,000 has to be paid. The maximum penalty is 10% of the tax unpaid.

The collection of GST from customer is a matter of agreement.

The supplier whether collects or not will still be liable to pay applicable GST to the government.