The app is the tool you will need to securely send/receive payment via QR Code Scanning, and to verify the service actually happened on the service providing platform, Adae. Scan once before the service, and scan once after. Each scan is time-stamped and proof of your start time and end time. This can be referenced in case of disputes/loss of payment.
For Flat Rate Services & Services Offering Products: only one scan is needed. Payment will be sent whenever this scan occurs.