Tax Codes cannot be read from the accounting system and need to be entered in XML format in the Accounting Settings Screen.
The format should be as follows.
<ArrayOfSupplierTaxCode>
<SupplierTaxCode>
<TaxCode>GST</TaxCode>
<Name>GST</Name>
<Percent>10</Percent>
</SupplierTaxCode>
<SupplierTaxCode>
<TaxCode>FRE</TaxCode>
<Name>GST Free</Name>
<Percent>0</Percent>
</SupplierTaxCode>
</ArrayOfSupplierTaxCode>