What are the government rules regarding the monthly tax period to be followed for GST entries?

According to the GST law, the monthly tax period for GST entries is the calendar month, i.e., from the 1st day to the last day of a month. However, there are some exceptions for certain types of taxpayers, such as: 
 Step 1: Composition taxpayers: They can opt for a quarterly tax period, i.e., from the 1st day of a quarter to the last day of the quarter. For example, the tax period for the quarter April-June is from 1st April to 30th June¹. 
 Step 2: Non-resident taxable persons: They can choose a tax period that is less than a month, depending on their duration of stay in India. For example, if a non-resident taxable person is in India from 15th May to 25th May, then the tax period will be from 15th May to 25th May. 
 Step 3: Casual taxable persons: They can also choose a tax period that is less than a month, depending on their validity of registration. For example, if a casual taxable person obtains registration for 20 days, then the tax period will be for 20 days. 
 The due date for filing GST returns depends on the type of return and the type of taxpayer. You can refer to this GST calendar or this GST return guide for more details on the due dates and forms of GST returns.