I am creating a sales order via SOAP and trying to specify the tax details. Tax calculations are being done in a separate app and just need to be recorded on the sales order. So far I have not been able to find a good reference describing the purpose of the various tax fields at both the line and body level. My attempted calls create the sales order record but it contains the default AvaTax values rather than what I specify. Has anyone done that successfully or know where documentation is located?

I could be wrong - but to pass your own rate you need to have a different tax code(s) and Use the 'Tax Amount Override' https://knowledge.avalara.com/bundle/upy1661872918927_upy1661872918927/page/ybk1665742958589.html

Thanks for the thought. I had come across that article as well which makes sense. Avalara uses a custom tax code and then sets the rate on each line. I similarly created a new tax code but have been unable to set the rate through SOAP calls. There are a few tax fields on the transaction line and many more at the transaction level as part of the TaxDetailsList.

I recommend creating a custom field on the header of the transaction to store the tax amount. Then creating a script that will take the value stored in the custom field and setting the tax override amount field.