Every bottle in the scheme carries a printed code. That code is what connects a physical bottle to a refund, and it can only be claimed once.
At the collection point the operator scans the customer’s UPI QR, then scans each bottle in turn. The system checks every code as it is scanned. A code that is not in the register, or one that has already been paid for, is refused straight away and the bottle is handed back. Accepted bottles are counted and the total is shown on screen.
When the customer is done, the refund is sent to their UPI ID. Only after the money has gone out is each bottle code closed, which means a failed payment never costs the customer their bottle – the codes stay valid until the refund succeeds.
Each collection is stored with its time, place and reference number, so an outlet can be reconciled at the end of the day and any individual payment traced.