I wholeheartedly endorse this suggestion. Some time ago, the DWP office in Belfast claimed not to have received my documents; when I phoned them I was told that they would send me another set and I would have to fill them out again. I remembered I'd sent them via recorded delivery (partly due to a mix-up at the post office counter), so I was able to go online and confirm via the Royal Mail site that my documents had been signed for the morning after I sent them. My having independent documentation to show that my documents had reached their office meant that the DWP staff were minded to search for them; a short while later, the missing documents were located.
