CSD refund entitlement: electronic filing with FORM RFD-10A, invoice validation and partial tax refund cap enforced. CSDs must file refund claims electronically in FORM GST RFD-10A on the common portal, applying quarterly (with an option to club quarters/FYs). Refunds are admissible only for inward supplies received from registered suppliers who have furnished GSTR-1 and filed GSTR-3B; invoices must show supplier GSTIN and CSD GSTIN and be accompanied by an undertaking and declaration. The proper officer will validate invoices against GSTR-2B/GSTR-1/GSTR-3B, exclude already-refunded invoices, ensure a partial tax refund cap, verify ITC reversals, and issue orders in FORM GST RFD-06 with a speaking order.