# Authentication methods overview

Source: https://developer.avalara.com/products/ecm/integration-guides/document-management/wvt8458608805161/

Guide: Exemption Certificate Management (ECM)

# Authentication methods overview

Learn about the authentication methods supported by AvaTax for API connections.

AvaTax uses [basic HTTP](https://en.wikipedia.org/wiki/Basic_access_authentication) authentication to connect to the API. Let’s describe exactly how to authenticate your API calls in AvaTax.

For HTTP Basic authentication, AvaTax supports two options:

-   Your AvaTax username and password

-   Your AvaTax account number and license key

Which style of authentication should you choose?

-   If you’re building a connector that customers will set up and use on their premises, use **Account ID/License Key** authentication; otherwise, use **Username/Password** authentication.

Below are examples showing how to use each approach.

-   **[Username and password authentication](/document-management/coa0890124811242/)**  
    Learn how to use username and password authentication with AvaTax, including constructing an authentication token.
-   **[License key authentication](/document-management/jwg4610283771454/)**  
    Learn how to use license keys for AvaTax account authentication.