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Once all 3 attributes are pre-filled then after when all orders within an order group have been are moved to dispatched state, a VAT invoice will automatically send to the specified email address. The trigger is the moving to dispatched so this won't happen if the orders are already in a dispatched state and you subsequently fulfil conditions 1-3 above.
If one of the above attributes isn't populated or corporate customer has a WineBank account then the invoice won't be automatically sent emailed out. The invoice also won't be sent emailed for any return, replacement or exchange orders.