"code": "BasicAuthIncorrect",
	"target": "Unknown",
	"details": [
			"code": "BasicAuthIncorrect",
			"number": 35,
			"message": "Incorrect Base header format.",
			"description": "The Basic header must be in the format 'Basic (Base64Encoded(value))' where Value is either 'username' + ':' + 'password' or 'accountid' + ':' + 'licensekey'.  -0-",
			"faultCode": "Client",
			"helpLink": "",
			"severity": "Exception"

This indicates that the Basic authorization header was not encoded correctly. The published standard for HTTP authorization headers specifies that Basic authentication is performed by setting the “Authorization” header in the HTTP request to the following string:

Basic Base64(credential + ':' + secret)

An example header looks like this:

Basic AhD72dhkS8=

In the HTTP request you provided to AvaTax, your information was not correctly encoded. Common troubleshooting steps:

  • Did you forget to provide either a username or a password?
  • Did you remember to put a colon in between your username and your password?
  • Did you forget to Base64 encode the resulting string?
  • Did you accidentally Base64 encode the word "Basic"?
  • Are you using a library that automatically handles this encoding for you, and you accidentally encoded the value twice?

For more information on authentication, please read Authentication in REST v2.