Collections software is often sold as speed. Speed is real, and it is also how a wrong bank account gets paid, or a write-off removes a balance the customer was about to settle. Maker-checker is the unfashionable rule that keeps speed from becoming a single point of failure.
The rule is small. The person who prepares a payment release, a write-off, or a change to bank details cannot be the person who approves it. That is all. It does not require a committee. It requires that the system refuse to let one login do both.
Where people try to route around it
Shared logins are the usual route around a control. So is an administrator role that everyone uses because the real roles were never set up. A useful access model names preparer, collector, approver, auditor, and administrator, and then makes the administrator reluctant: able to grant access, and not the daily way to approve a payment.
Auditors do not need to approve anything. They need to read. Giving them a collector’s seat so they can “just look” is how a read-only question becomes an accidental send.
Signals are not decisions
A duplicate invoice, a new bank account, or an amount that does not resemble the last six is a reason to stop and show the evidence. It is not a reason for software to quietly refuse a customer and leave no explanation. The checker should see the signal, the underlying documents, and a place to write why they cleared it or why they did not.
That written reason is the part people skip, and the part they want six months later. A cleared flag with no sentence is just a button that was pressed.