[pieno]

Most bank transfers are actually not reversible, except for some limited retail client (including small companies) operations where specific terms & conditions allow the bank to reverse payments to the extent possible, which they really prefer avoid using as it looks really bad for a bank whose most important asset is the confidence of its clients and counterparties. Reversal may also no longer be possible if the money has already gone out in a system that does not allow reversal, or if the client is bankrupt in the meantime (depending on local banking and bankruptcy laws and circumstances).

For any other payment system for larger sums / corporate and institutional parties, settlement finality is a huge thing that is the subject of all sorts of specific legislation, as it would be a real issue for the health of the financial system if a settled payment can simply be reversed, as it would have a lot of unintended consequences further down the line. So banks actually do have strict risk management policies to avoid wrong payments, but there are so many complex transactions for which ultimately a human (actually at least 2 due to 4-eyes principles) must confirm whether conditions for payment are satisfied and whether payment details are correct, and humans are always prone to making mistakes once in a while.

[tumetab1]

I didn't make myself clear, I wanted to mean that transfer are reversible (with the cooperation of the other bank) not that the source bank can unilaterally do it.

The law sides with the banking making the mistake as discussed on https://news.ycombinator.com/item?id=24222045

With bank cooperation, which usually happens, settlement are non-issues. When an operation can be reversed by one of parties the settlement agreement usually mentions that the settlement is only final when the reversion period is over.