When creating Sales Order / Estimate via API, the line item Tax Code does not get pulled in.

When creating Sales Order / Estimate via API, the line item Tax Code does not get pulled in.

I'm creating Sales Orders via API from CRM but it does not pull in the "Tax Code"

I've read within the forums that this should be done automatically but it's not happening.

Not sure if it's a bug or by design?
Anybody else know?
Should we be adding the Tax code via API also?

Thanks in advance!

Note: We use Avalara integration