> ## Documentation Index
> Fetch the complete documentation index at: https://polar-rishi-raj-jain-patch-2.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Billing

> How billing works with Usage Based

## Metered Pricing

Metered Pricing is a pricing model where you charge your customers based on the usage of your application.

There are a few different pricing models unique to Usage Based Billing:

* Unit Pricing
* Volume Pricing *(coming soon)*

### Unit Pricing

Unit pricing is a simple pricing model where you charge a fixed amount for each unit of usage.

For example:

| Product Meter       | Price per unit |
| ------------------- | -------------- |
| `prompt-tokens`     | \$0.10         |
| `completion-tokens` | \$0.18         |

This means that every unit of `prompt-tokens` consumed by a customer will be charged at \$0.10 and every unit of `completion-tokens` will be charged at \$0.18.

It's a linear pricing model, where the price per unit is fixed.

### Volume Pricing *(coming soon)*

Volume pricing is a pricing model where you charge a fixed amount for a certain volume of usage. Volume pricing is not yet available, but will be coming soon.

## Invoicing Customers for Usage

Our Usage Based Billing infrastructure is built to work with Subscription products out of the box.

### Add a metered price to your product

To charge your customers for usage, you need to add a metered price to your product. You'll need the select the **Meter** and the **amount per unit**.

<img className="block dark:hidden" src="https://mintlify.s3.us-west-1.amazonaws.com/polar-rishi-raj-jain-patch-2/assets/features/usage/cap.light.png" />

<img className="hidden dark:block" src="https://mintlify.s3.us-west-1.amazonaws.com/polar-rishi-raj-jain-patch-2/assets/features/usage/cap.dark.png" />

Optionally, you can set a **cap**. The customer will be charged the cap amount if they exceed it, regardless of the usage.

### Monthly Invoicing

If a customer has a subscription with a monthly billing period, usage is aggregated monthly and invoiced at the end of the month with the rest of the subscription.

### Yearly Invoicing

If a customer has a subscription with a yearly billing period, usage is aggregated yearly and invoiced at the end of the year with the rest of the subscription.

<Warning>
  If a [discount](/features/discounts) is applied on the subscription, it'll be
  applied on the **whole invoice**, including metered usage.
</Warning>

## Customer Portal

Customers can view their estimated charges for each meter in the Customer Portal.

<img className="block dark:hidden" src="https://mintlify.s3.us-west-1.amazonaws.com/polar-rishi-raj-jain-patch-2/assets/features/usage/portal.light.png" />

<img className="hidden dark:block" src="https://mintlify.s3.us-west-1.amazonaws.com/polar-rishi-raj-jain-patch-2/assets/features/usage/portal.dark.png" />