Credit Note On GST

A business issued a consultancy invoice in February 2025, but the client paid only the base amount, excluding GST and TDS, claiming they never received the invoice. The client now requests a credit note and invoice for the 2025-26 financial year, despite the original GST having already been paid and filed. The core issue is how to correctly issue a credit note referencing the original invoice when the client disputes its receipt and hasn't accounted for the GST.