There are three ways where you can delete a document on the online application: 

Documents can be deleted in the home-screen. Select a document and then click on the trash-bin icon on the top right of the page to delete the document.

When you are in the booking-screen, there are three options on the upper left of the page. Click on the trash-bin icon to delete the document.

You can delete a document in the Archive by selecting the document first and the option Abandon will appear on the top menu. You can click on Abandon to delete the selected document. If the Abandon option is not available in the menu, it is not possible to delete the document.

In the archive, you can find all the deleted document under the Document Status and then select the option Abandoned.  All deleted documents are shown on the right side of the page. When you can click on it, it will open the invoice and then click on Document Timeline to see the reason why it was deleted.

If a document has a lock-icon as the status, it is no longer possible to delete the document because the document is already booked to the accounting package.