Ok I am relatively new to billing. I know that a G0402 needs to be done within 12 months of Medicare enrollment, and I know that a G0438 needs to be done 1 year after that, then G0439 every year after. Here is my question: I have a whole bunch of encounters where I need to crosswalk preventative checkup codes to G-codes, and the encounter has all the proper documentation for a G0439, but there is a problem: We never billed out a G0402 or G0438 and it is long past the one year mark after enrollment (or they had Medicare before coming into our health system). Can I still bill out a G0439 if we never billed out a G0402 or G0438?