Late invoices are not a collections problem; they are a reminders problem until the moment they aren't. The first two nudges land friendly, on the channel the AP contact uses for everything else, and they include the PDF, the payment link, and the line item being asked about. By day fifteen the tone tightens and the cadence shifts. By day forty-five the sequence escalates into a human-touch workflow rather than another automated email nobody will open.
Dunning sequences in 4notify branch on invoice amount, customer tier, and prior payment behaviour. A holdout group is supported so finance can measure incremental recovery rather than guessing whether the reminders moved the needle, and the audit log keeps every send, retry and delivery code in case the dispute ever lands in a courtroom.