A GST report is a document containing details of all income/sales and/or expense/purchase which a taxpayer (every GSTIN) is required to file with the tax administrative authorities. This is used by tax authorities to calculate net tax liability. To file GST reports or for GST filing, check out gst.cleartax.in website that allows import of data from various ERP systems such as Tally, Busy, custom excel, to name a few. Moreover, there is option to use desktop app for Tally users to directly upload data and filing. If GST reports are not filed within time, you will be liable to pay interest and a late fee.