"code": "DocumentCodeConflict",
	"target": "Unknown",
	"details": [
			"code": "DocumentCodeConflict",
			"number": 303,
			"message": "Please specify DocumentType parameter",
			"description": "This API applies to a single document, but multiple documents exist for company '-0-' and code '-1-'.  Please provide the DocumentType parameter to distinguish between them.",
			"faultCode": "Client",
			"helpLink": "",
			"severity": "Error"

This error indicates that you attempted to create a document with a code that matches an existing transaction.

In AvaTax, a committed transaction is considered “finalized,” and its transaction code is reserved and may not be reused.

If a transaction is not yet committed, you can continue to update it by re-creating a document with the same code as many times as required.

Once a transaction has been committed, you can either adjust it by calling the POST /api/v2/companies/(code)/transaction/(code)/adjust endpoint or you can void it by calling the POST /api/v2/companies/(code)/transaction/(code)/void endpoint.

Transactions that have been reported to a tax authority cannot be adjusted, voided, or altered in any way. To modify a transaction that has been reported to a tax authority, create a reverse transaction with amounts opposite the original transaction.