Hi Guest! I am not aware of any rules that insurers must process “D” codes when a direct crosscode is not available. Some medical insurers will accept codes like 41899 for services that do not have a direct crosscode available. 41899 stands for: Unlisted procedure, dentoalveolar structures …and the explanation of the service the code is being used to represent can be provided in a narrative report, and/or by using the ZZ qualifier with a short narrative description in the supplemental information (the red shaded line that is typically left blank) on the claim form on the the line items in field 24j. Hope this helps!