> This page is for Documentation, version Integration guides (default).
> For other versions, use one of these documentation indexes:
> - Integration guides (default): https://avalara.ferndocs.com/docs/integration-guides/llms.txt
> - Refactor guides: https://avalara.ferndocs.com/docs/refactor-guides/llms.txt
> - Get certified: https://avalara.ferndocs.com/docs/get-certified/llms.txt
> - Agent to Agent (A2A): https://avalara.ferndocs.com/docs/agent-to-agent-a2a/llms.txt
> - AI use cases: https://avalara.ferndocs.com/docs/ai-use-cases/llms.txt
> - API versioning: https://avalara.ferndocs.com/docs/api-versioning/llms.txt

> For clean Markdown of any page, append .md to the page URL.
> For a complete documentation index, see https://avalara.ferndocs.com/llms.txt.
> For AI client integration (Claude Code, Cursor, etc.), connect to the MCP server at https://avalara.ferndocs.com/_mcp/server.

# Authentication

This first task describes authenticating in AvaTax using the API, including the available authentication methods. It also provides helpful information about AvaTax's two environments: [Sandbox](http://sandbox.admin.avalara.com/ "AvaTax Sandbox") and [Production](http://admin.avalara.com/).

If you know the authentication method you're going to use, and you’re ready to authenticate, you can skip to the [Ping the server](ping.htm) section.

> **Note**
>
> Part of the **VAT for Ecommerce** integration guide. [Open the full "Authentication" milestone on Avalara](https://developer.avalara.com/vat-ecom/authentication-in-avatax/) to see every page in this section.