Q Can a challan generated online be modified?
Ans. No. After logging into GSTN portal for generation of challan, payment particulars have to be fed in by the tax payer or his authorized person. He can save the challan midway for future updation. However once the challan is finalized and CPIN generated, no further changes can be made to it by the taxpayer.
Education Guide on Goods & Service Tax (GST)