e-Challan format for GST payments will serve as the official payment source, shared real-time with bank systems. e-Challan is the primary source document for GST payment accounting and reconciliation, to be provided in a prescribed format and treated as proof of payment. Challan data will be shared in real time from the GSTN portal to the authorized bank's Core Banking System or RBI, removing branch-level data entry. The GAR form will require modification for electronic use, and absence of a jurisdictional location code on the challan necessitates mapping via each tax administration's backend systems for accurate receipt classification.