Does the order have a tax rate? (See Customer Defaults - Financial)
If not, confirm if the customer has a default tax rate set?
- If yes, edit the order and add the tax rate.
- If no, edit the customer and add one for future orders, edit the order and add the tax rate.
Does the shipment have a tax rate? (See Orders - Creating a Shipment)
If yes, does the order have a shipment?
- If items are allocated on a shipment. then the tax is calculated off that. Ensure the shipment has a tax rate.