Step 1: Download reports from Amazon and Flipkart.
Step 2: Upload these reports in TaxAdda GST Software for Online Sellers
Step 3: Add offlines sales and purchase, if any.
Step 4: Generate GST Returns and download in json format.
Step 5: Upload json file on GST portal.
Yes, GST is mandatory to sell on online websites like Amazon, Flipkart etc. If you sell only via your own website or facebook/instagram then you can sell without GST registration but only in your own state.
You have to just upload the reports downloaded from these platforms and upload in TaxAdda GST software and software will calculate the GST amount payable.
Yes, you can take the input tax credit of GST paid on commission or other charges like advertisements, courier etc to Amazon, Flipkart or other online platform.