When I hit view invoice, close the invoice (with the x in the top right corner), and hit view invoice again, the invoice is all grey, as if it disappeared. I can get the invoice back again by reloading the page. This is on a fully up to date Mac with Safari. The Duck Duck Go browser behaves the same way. But on Chrome, the invoice is not lost. To me, that means you have buggy software, and I do not fully trust it. I have told this to the vendor, and recommend that he get another backend accounting software vendor.