TL;DRThe configured sequence of reminders that runs on an unpaid invoice until cash lands.
A cadence says: three days after due, a polite note; at day seven, a firmer one; at day fourteen, escalate. It is configured once with merge fields for the number, amount, and due date, and runs on every eligible invoice.
Payment is the off switch. A promise to pay holds the cadence; a partial payment pauses it. Every message sent is kept on the invoice's thread.
Where it happens in Sonic
Next
See it on your contracts
A walkthrough on the agreements and files you actually bill from — not a slide deck.