You can control who can export invoices. 

You can choose who will see the export icon and tick boxes. To do this, head to Business >Settings > Validation

Manual Exporting of Invoices

From here, you can multiple select the users that can export invoice. Only users with the Finance role will be displayed here. Exporting invoices is usually the role of someone in Finance. 

If you cannot see the Export button and tick boxes when you are viewing the Invoice page, then you need to ask you Zahara administrator to adjust the settings as above.