Payment rails
Irrevocability
The property of a settled payment that can no longer be unilaterally cancelled by its sender.
Once a transfer is settled the sender cannot take it back. They can ask the beneficiary to return the funds, or start a recall procedure the beneficiary is free to refuse, but there is no cancel button.
That property is the corollary of speed: it is because settlement is final that the beneficiary can use the funds immediately. It explains why upfront validation — check digits, name resolution — carries the whole weight of safety on instant rails.