when i bill out insuranace that requires xrays or periocharting, we are old school and have paper charts, i would either put CMP and circle it, so when the ins company sent a letter back asking for such documentation, I would tell them "No, I have sent the requesting missing info already." because i could check the chart, see the CMP (copy, print, mail) in the chart. They would put me on hold and usually find it.
once i billed the insurance, I would place an I, then circle it, telling me I had billed it, then place it in our pending cart by month, in alphabetical order.
So by the end of the month if something hadn't been paid, i could call the ins comp. and ask them why or what is missing or if they even received it.. if not, i would re-verify the address, id # patient information etc.
Hope this helps a little.