We had a custom field “Missing Itemized Receipt” check box configured into our forms for certain expense types. The form is visible to the expense processor and approving manager only, not the user creating the expense report. We also requested that this custom field have the ability to be reported on.
We trained the expense processors to check the Missing Itemized receipt checkbox as needed as part of their review process.
As Administrator or our Concur system, I pull reporting quarterly on missing itemized receipts and all users who have multiple missing itemized receipts are sent a reminder of the IRS/Corporate guidelines regarding itemized receipts.