# AvaTax error messages

Source: https://developer.avalara.com/products/ecm/integration-guides/document-management/urj1349489476804/

Guide: Exemption Certificate Management (ECM)

# AvaTax error messages

Understand AvaTax error messages, their causes, and how to address them.

The [AvaTax error messages](https://developer.avalara.com/avatax/errors/) are designed to explain what went wrong during an API call, what actions you can take, and how to proceed.

When an AvaTax API call produces an error, it responds using standard [HTTP error response codes](https://en.wikipedia.org/wiki/List_of_HTTP_status_codes). These codes fall into two categories:

-   **Client Errors (400–499):** Indicate a mistake in the API call.
-   **Internal Errors (500–599):** Refer to issues within AvaTax. These errors are automatically logged and reported to the development team for resolution.

If your program receives an HTTP response code between 400 and 499, follow these steps:

1.  Parse the error message using a JSON parsing engine.
2.  Display the error summary to the user.
3.  Link the user to the documentation page that explains the error.
4.  Allow the user to modify their request or retry the action.

For example, if an AvaTax API call fails to include authentication credentials, the user will see the error message [AuthenticationIncomplete](https://developer.avalara.com/avatax/errors/AuthenticationIncomplete).