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

# Application Billing API

> Server-side APIs for customer, subscription, checkout, invoice, and usage workflows

The Application Billing API covers the workflows most integrations need: customer provisioning, plan discovery, subscriptions, payment-gated checkout, cancellation, invoices, and usage events.

## Base URL

```
https://core.nozle.app/api/v1
```

## Authentication

All Billing API requests require a Bearer token:

```
Authorization: Bearer YOUR_BILLING_API_KEY
```

Get your billing API key from the Nozle dashboard under **Settings > API Keys**.

## Resources

<CardGroup cols={2}>
  <Card title="Customers" href="/api/create-customer" icon="users">
    Create, update, and manage customers
  </Card>

  <Card title="Events" href="/api/events" icon="bolt">
    Send usage events for metering
  </Card>

  <Card title="Subscriptions" href="/api/subscribe" icon="repeat">
    Assign plans to customers
  </Card>

  <Card title="Plans" href="/api/list-plans" icon="clipboard-list">
    Define pricing and charges
  </Card>

  <Card title="Invoices" href="/api/list-invoices" icon="file-invoice">
    Retrieve customer invoices
  </Card>

  <Card title="Wallets" href="/api/credit-balance" icon="wallet">
    Legacy prepaid balances
  </Card>
</CardGroup>

<Info>
  Use the [Nozle API](/api/authentication) for higher-level checkout, product-credit, entitlement, and margin-intelligence endpoints.
</Info>