RuleMustHaveTaxCode
Example
{
	"code": "RuleMustHaveTaxCode",
	"target": "Unknown",
	"details": [
		{
			"code": "RuleMustHaveTaxCode",
			"number": 82,
			"message": "A product taxability rule must be assigned to a specific tax code",
			"description": "The rule type 'ProductTaxabilityRule' must be assigned to a specific tax code.  It cannot be assigned to a null tax code or to all tax codes.  Please try creating the rule again with a tax code value.",
			"faultCode": "Client",
			"helpLink": "http://developer.avalara.com/avatax/errors/RuleMustHaveTaxCode",
			"severity": "Error"
		}
	]
}
Explanation

A tax rule with type ProductTaxabilityRule cannot have a null tax code or be assigned to all tax codes. When creating a TaxRule with type ProductTaxabilityRule, a specific TaxCode must be included. The TaxCode field is optional in some cases, but leaving TaxCode and TaxCodeId fields empty will result in an error. To search for appropriate tax codes, use the ListTaxCodesByCompany API. You may also use the Avalara Tax Code Search page.