• When you’re calculating tax on returns or credit memos, there are a few things to keep in mind:

    • Avalara Avatax makes no direct association to the original invoice. That’s handled by you and your application.

    • Send us negative extended sale amounts (qty * price) on your line items. This will make us calculate negative liability. Quantity should always be a positive value and price should always be negative to ensure that the amount is negative.

    • Keep an eye on your DocCode. You can use the same DocCode as your original invoice exactly once if you send the return with DocType ReturnInvoice, but make sure you think about multiple returns associated with the same invoice.

    • Dates. You want to report the return in the period in which it was processed, but it may have calculated tax in a previous period (which had different tax rates). To handle this, send the DocDate as the date of return processing, and use TaxOverride.TaxDate to send the date of the original invoice.

    • Return Invoice or Credit Memo processing is largely a business practice that the business manager needs  to map. 

    • To see more information and an example of the process go to: http://developer.avalara.com/api-doc...eturn-invoices