We are forced to use our own scripts instead of your inbuilt Xero integration due to limitations with the way tax is applied to synced invoice.
From Invoiced we should be able to select the tax rate that's used within Xero such that when it gets synced across it applies the correct one.
For example, when an Australia customer is invoiced it should select "GST on Income". When a New Zealand customer is invoiced it should select "GST Free Import".
We should be able to map these based on the Tax rules.