PBI controller expressed concern regarding MIA TRACON'S failure to insure the correct beacon codes; i.e. IFR vs. VFR; are entered into the NAS prior to any hand off attempts; providing an example of such an occurrence.

Narrative

MIA Approach had typed Aircraft X into the NAS (National Airspace System) for VFR flight following from the MIA area to SFB. The NAS code was 37XX and the flight was active under this code. At some point MIA changed the aircraft code to 43XX and issued him an IFR clearance to SFB; direct at 6000ft. Since the VFR flight plan was active the aircraft would not tag and MIA called for a manual hand off. I took the information but was never told the aircraft was IFR. Because of the 43XX code; I assumed he was VFR. When the aircraft checked on my frequency level at 6000ft I inquired as to whether he was IFR or VFR. He informed me that he had been issued an IFR clearance. I then had to return him to his NAS code of 37XX and amend the flight plan to IFR and a correct routing. Without the NAS code the aircraft would require a manual hand off from me to ZMA and would not receive MSAW processing throughout his route. Recommendation; train MIA Approach to the fact that their 43XX codes are a local subset only. They are to be used in house only. If they are going to issue IFR clearances to VFR aircraft; they need to either amend the VFR flight plan or remove it and start over. This is the 4th time in the past month that I have seen this exact scenario. Apparently MIA training is not teaching the controllers how the NAS works.