Goods and Services Tax Network GSTN ), the IT backbone of the new tax regime, today said it has put a new function on its portal to allow taxpayers choose the frequency of filing GSTR 1 form on quarterly or monthly basis.Taxpayers with annual aggregate turnover up to Rs 1.5 crore in the previous financial year or anticipated in the current financial year can avail the option of filing quarterly returns.Form GSTR 1 summarises all the sales of a taxpayer.This has been done as per decision taken in the 23rd GST Council Meeting. After giving their option, taxpayers can file GSTR 1 for the relevant return periods, the Goods and Services Tax (GST) Networks said in a statement.It further said that taxpayers who opt for quarterly filing will have to select the last month of the quarter from the drop down menu.Further, all taxpayers who opt for monthly filing can now file GSTR 1 from August onwards till November. Filing of return of previous month is mandatory.GSTN has been set up to provide IT infrastructure and services to the central as well as state governments, taxpayers and other stakeholders for implementation of the GST, which came into force on July 1 this year.