How to apply multiple charge models to the same billable metric

You can put several charges on one plan that all reference the same billable metric, each using a different charge model. There is no need to duplicate the metric or send the event twice. Each charge is calculated independently from the same event stream and billed as its own line item.

How it works

When an event is ingested, Lago looks at the active subscription's plan and finds every charge that references the event's billable metric code. It processes each of those charges on its own. If a plan has two charges pointing to the same metric, for example one percentage charge and one graduated charge, both are calculated from the same events and appear separately on the invoice.

How to set it up

Add each charge to the plan in the dashboard or via the API, give each one the charge model you want, and point all of them at the same billable metric. Any event sent with that metric's code then feeds every matching charge automatically.

When you add a second charge for a metric already used on the plan, the dashboard shows a warning: "Metric already used in the plan, customers will be charged several times." This is a confirmation, not an error. It is telling you that both charges will apply, so make sure billing the metric more than once is what you intend before you continue.

This article reflects guidance drawn from customer case resolutions. It is not officially supported documentation and may not apply to all situations.