TL;DRA document that gives money back against an issued invoice instead of editing it.
When a customer downgrades mid-period, or a sent invoice over-billed, the unused value is returned as a credit note that references the original. The original stays exactly as it was sent.
Unused-time credits walk calendar units of the price basis — a full month credited on a quarterly invoice is exactly one month's price, not a fraction of days.
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.