AvaTax transaction state matters as much as the returned calculation. Avalara distinguishes temporary SalesOrder estimates from persistent SalesInvoice transactions and explains when transactions become reportable.
For the Avalara integration, model quote, invoice and commit as separate application steps. Exercise them with synthetic transactions in the appropriate test environment, including cancellation and retry paths. This is an API lifecycle check, not a determination of which taxes a particular business owes.
Akousa