Proration
TL;DRCharging or crediting only the part of a period a customer actually had something.
A seat added on the 20th should not cost a full month. A plan upgraded on the 15th should charge the difference for the rest of the period only. Proration is that arithmetic.
Sonic prorates by calendar units of the price basis: a monthly price is walked month by month, with only the partial month scaled by its days. Dividing a quarterly amount by 90 days is a shortcut that produces different numbers, and it is not what the platform does.
The proration policy on a seat product decides which events are prorated at all — none, added seats only, or added and removed seats.
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.