Refund acknowledgement triggers the statutory time limit, requiring portal forms for filing and deficiency notices. Refund acknowledgement must be provided electronically via the Common Portal in FORM GST RFD-02, and the statutory time period under section 54(7) is counted from that filing date. The proper officer shall scrutinize non electronic cash ledger refund applications for completeness and issue the same acknowledgement when complete; exports of goods attract expedited acknowledgement. Deficiencies are to be communicated through FORM GST RFD-03 electronically, and deficiencies communicated under CGST/SGST rules are also deemed communicated under this rule.