GSTN had made available below APIs as Public API which can be accessed by the public without requiring taxpayer's authentication.
Track GST Return API lets you view E-filled returns. This tool can help buyers check the tax payment status of their suppliers and make claiming the input tax credit (ITC) easier.
Search GSTIN API lets you verify GSTIN in real-time. GST number or GSTIN i.e. GST Identification Number is a unique number issued to a business registered under GST. It is a 15 digit number allotted on the basis of the PAN of the business. GSTIN can be verified on the GST Portal. It is important to verify the GSTIN of a taxpayer to ensure that the GSTIN quoted by them on the documents actually belongs to them. Further, it is important to ensure that the GSTIN on the invoice is valid since many sellers enter a fake GSTIN to fraudulently charge GST from the buyers. If the GSTIN provided is incorrect, then you will get an error message. If correct you will see the details attached to the GSTIN.