What happens when this goes wrong?
Every other page shows this payment working. Here you choose what breaks, and follow the damage — because a hold, a return or a missed cut-off is the system working as designed, and reading one calmly is the job.
Pick a failure above. Nothing here is invented — each one is a reason code this rail really uses, at the step where it really strikes.
This diagram shows one payment between two banks; it omits NPP's overlay services, connector and identified-institution roles, and the exact PayID registry and messaging mechanics. Every failure here is authored on Australia NPP — real-time settlement via the Fast Settlement Service, with the sources that back it.