Hi, How to stop saving of invoice at Supplier Portal when clicking Calculate Tax option in Action me

When Supplier is trying to create invoice through supplier portal then there is a “Calculate Tax” option on invoice. When supplier is clicking on “Calculate Tax” then system is automatically saving this invoice as “Incomplete” invoice even though this invoice is saved. This is creating issues with supplier and us. Supplier thinks that invoice is completed although it is not complete. Pleases suggest how system should not save the invoice when supplier clicks the “Calculate Tax” option in the Action menu at Create Invoice UI of Supplier Portal.