Financial software operates under a different moral contract than other software.
A bug in a social media app loses a post. A bug in a banking ledger loses someone's money. Possibly their livelihood.
Double-entry accounting is a verification philosophy: every action must produce a matching, auditable counteraction. If the system cannot prove balance, it must refuse to proceed.
I apply this beyond finance now. Every critical system has a counterpart check. Every write has a verify. Every transaction is atomic or it does not happen.
When the stakes are real, the code must be correct. Not approximately correct. Correct.
— Dick Bassey | DevDick | 2010