> ## Documentation Index
> Fetch the complete documentation index at: https://docs.sequencehq.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Per-event billing

> Generate a separate invoice for every usage event

Per-event billing generates a separate invoice for **every usage event** you submit. As soon as an event is received, it is billed on its own, so one event produces one invoice. This is ideal when each event represents a discrete, individually-billable transaction and you want the invoice to map exactly to the event that triggered it.

### How per-event billing works

<Icon icon="check" iconType="solid" /> Every usage event generates its own invoice (one event, one invoice)<br />
<Icon icon="check" iconType="solid" /> Invoices are generated as soon as the event is received<br />
<Icon icon="check" iconType="solid" /> Set per product, so a single billing schedule can mix per-event and other billing frequencies<br />

### How it differs from on-demand billing

[On-demand billing](/billing/on-demand-billing) **aggregates** usage over a window (hourly or daily) and produces one invoice per window. Per-event billing does **not** aggregate. Each event is billed independently and immediately.

|                                    | On-demand (hourly/daily)                          | Per-event                          |
| ---------------------------------- | ------------------------------------------------- | ---------------------------------- |
| Invoice grouping                   | One invoice per hour/day window                   | One invoice per event              |
| Timing                             | At the close of each window                       | As soon as the event is received   |
| Deduplication by `customerEventId` | Yes, only the latest event in a window is counted | **No**, every submission is billed |

### Getting started with per-event billing

1. Create a usage metric.
2. Configure a product and price with a usage-based pricing model.
3. Set the billing frequency to `per-event` on the product.
4. Create and start a billing schedule including the new price.
5. Submit an event for the customer and metric used in the price.
6. An invoice is generated for that event as soon as it is received.

<Note>Per-event billing is only compatible with usage-based pricing models. It is configured per product, so you can mix per-event products and [on-demand](/billing/on-demand-billing) products within the same billing schedule.</Note>

### Deduplication and re-submitting events

<Warning>
  **Per-event billing does not deduplicate by `customerEventId`.** Because every submission is billed on its own, re-sending an event with the same `customerEventId` generates an **additional** invoice rather than replacing the original, and re-sending with a changed `eventTimestamp` charges the customer again. This differs from monthly and on-demand billing, where only the latest event for each `customerEventId` is counted.

  As a result, **`customerEventId` cannot be used as an idempotency key with per-event billing.** Only submit an event once, and do not attempt to correct an event by re-submitting it. Contact support to correct an already-issued invoice.
</Warning>

### Example use cases

* **Transactional billing**: Bill customers for each individual transaction as it happens
* **One-to-one invoicing**: Where each event must map to exactly one invoice for reconciliation

### Frequently asked questions

<AccordionGroup>
  <Accordion title="When are invoices generated?">
    An invoice is generated for each event as soon as it is received. There is no aggregation window.
  </Accordion>

  <Accordion title="What happens if I send the same event twice?">
    Both submissions are billed, producing two invoices. Per-event billing does not deduplicate by `customerEventId`, so only submit each event once. Contact support to correct an already-issued invoice.
  </Accordion>

  <Accordion title="Can I mix per-event and on-demand billing?">
    Yes. Billing frequency is set per product, so a single billing schedule can include some products billed per-event and others billed on-demand.
  </Accordion>

  <Accordion title="Can I use this with fixed pricing models?">
    No. Per-event billing is only available for usage-based prices.
  </Accordion>
</AccordionGroup>