"code": "DuplicateSystemTaxCode",
	"target": "Unknown",
	"details": [
			"code": "DuplicateSystemTaxCode",
			"number": 155,
			"message": "Taxcode -0- already exists.",
			"description": "This tax code already exists in Avatax and cannot be duplicated. Please designate a different tax code identifier.",
			"faultCode": "Client",
			"helpLink": "http://developer.avalara.com/avatax/errors/DuplicateSystemTaxCode",
			"severity": "Error"

This error indicates that you attempted to create a duplicate TaxCode object. In AvaTax, each tax code is expected to have a unique name. When you create a new tax code, you should not reuse an existing tax code string.

For example, the AvaTax system tax code P0000000 refers to general tangible personal property. In order to reduce confusion, you are not permitted to create a custom tax code that shares the same name as this tax code. Please choose a new, unique, tax code.