In the GST regime, any regular business has to submit two monthly returns and an annual return. This equals 26 returns in a year.
The beauty of the system is that one has to manually enter the details of a monthly return: GSTR-1. The other GSTR 3B refund will be automatically completed when you obtain information from GSTR-1 submitted by you and your suppliers.
There are separate returns that must be presented in special cases, such as distributors of compositions.