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# Provider APIs

Provider APIs use a reverse data flow — BigCommerce calls *your* app's endpoints to retrieve data on behalf of a store. These are API specifications that your application must implement, not APIs you call directly.

## Authentication

Each provider type has its own authentication model:

### Shipping Provider

Developer-configured authentication. When you register your carrier with BigCommerce, you define a carrier configuration schema. BigCommerce includes the merchant's configuration values in each request payload. How you authenticate stores is up to your implementation.

### Tax Provider

Uses HTTP Basic Authentication. Your app establishes a connection via the Tax Provider Connection API, supplying a username and password. BigCommerce sends these credentials in the `Authorization` header when calling your endpoints.

For additional context, see [Authentication overview](/developer/docs/overview/api-fundamentals/api-accounts#developer-configured-authentication).

## What's inside

* **Shipping Provider** — Rate quote requests and connection validation endpoints that your app implements
* **Tax Provider** — Tax estimate, commit, adjustment, and void endpoints, plus the Tax Provider Connection API for managing connections

## Prerequisites

You must be a registered single-click app in the [BigCommerce Developer Portal](https://build.bigcommerce.com). After registering your app and implementing the required endpoints, contact BigCommerce to receive a carrier or provider ID.

## Getting started

1. Register a single-click app in the Developer Portal
2. Implement the required endpoints per the API specification
3. Contact BigCommerce to receive your carrier/provider ID
4. Merchants install your app from the BigCommerce control panel

## Related resources

* [Shipping developer guide](/developer/docs/integrations/shipping-providers)
* [Tax developer guide](/developer/docs/integrations/tax-providers)