Over the counter GST payment: bank-portal integration enables real time challan verification and two stage payment confirmation to taxpayers. OTC GST payments require taxpayers to generate a finalized challan on GSTN with a unique CPIN valid for seven days; GSTN shares challan data in real time with the bank CBS. Authorized banks must deploy customized IT to accept OTC receipts, verify CPIN at the teller, and either credit a GST pool account then allocate to tax heads or credit respective tax accounts directly. Banks must send an initial intimation on tendering and a second message upon realization (including CIN and BRN) so GSTN can update taxpayer ledgers and notify taxpayers; dishonours must be reported.