Overage
Usage beyond an included allowance or commitment, billed at a separate — often higher — rate.
Overage is usage that exceeds an included allowance or a committed volume, billed separately — usually at a higher per-unit rate than the base allotment covers.
It matters because overage is where usage-based pricing earns its name: a plan's base fee or commitment sets a predictable floor, and overage is the mechanism that captures additional value as a customer's usage grows, without needing them to jump to a new plan tier every time they cross a line.
In practice, overage is calculated by comparing metered usage in a billing period against the included allowance or commitment, then applying the overage rate to whatever's left over — the same metering data that tracks 'usage so far' drives both the in-app warning a customer sees and the final invoice line.
The common pitfall is surprise: a customer who only sees their overage charge on the invoice, with no visibility into how close they were running to the line beforehand, experiences it as an unexpected charge rather than a predictable consequence of their own usage. Surfacing a real-time meter and a projected month-end total avoids that surprise entirely.