TL;DRA mid-term change to what a customer is billed — proposed, reviewed, then applied.
More seats, a higher tier, a product removed, a price renegotiated: an amendment changes the schedule from a date forward. Sonic treats it as a proposal first, shows the before-and-after for the affected window, and only makes it real when someone approves.
What it produces depends on the invoices involved. An open draft is edited in place. A sent invoice is never rewritten; the difference becomes an adjustment invoice or a credit note alongside it.
Where it happens in Sonic
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See it on your contracts
A walkthrough on the agreements and files you actually bill from — not a slide deck.