When you initially connect to Xero, Invitbox will automatically import all your Xero defined tax rates.
Managing your Tax Rates and setting defaults
Once your tax rates are uploaded into Invitbox you need to choose two Xero tax rates to act as the defaults for taxable and non-taxable items. This means that when invitbox detects an item is taxable or non-taxable, it will use these defaults to send with the bill/line-data to Xero, this is unless you choose to manually assign a different non-default tax rate to the item via the invoice. For further information on assigning non-default tax rates to a bill, see here
To choose your 2 defaults go to the Admin Tab > Tax Rates > edit.
The below image shows what a typical setup looks like. We have ticked the 2 standard tax rates (GST 10% and GST Free)