Air taxi Captain reported FMS displayed an incorrect route track that disagreed with secondary navigation and ATC resulted in GPS misdirecting aircraft. Captain also stated the GPS source lost integrity or possible corruption; yet Captain showed no indication.

Narrative

I was the PIC of Aircraft X operating under Part 135 charter regulations on a daytime IFR flight. Approximately 10 milesinto the en route portion of the flight; we experienced a GPS anomaly that caused the aircraft's position to appear offset on the navigation display. At the time; we were operating in Class G/E at 12000'MSL; with clear VMC conditions.Shortly before crossing baats; ATC advised us to make a turn towards baats. Our flight management system (FMS) was showing us on the correct routing; but our secondary navigation sources confirmed that baats was at a different location. We cross-checked with raw data (VOR/DME) and verified the discrepancy.We immediately corrected the course manually using traditional navigation references and coordinated with ATC and told them the issue. No traffic conflict occurred; and the remainder of the flight was uneventful.Upon post-flight review; it appeared that our GPS source briefly lost integrity or became corrupted; but no annunciation appeared on the PFD (Primary Flight Display) or MFD (Multi-function Flight Display). No NOTAMs were published for known GPS interference in the area at the time.Contributing Factors:Temporary GPS signal degradation or spoofing/interferenceOver-reliance on FMS data before cross-checking with raw navigation aidsThis event highlighted the importance of regular cross-checking of GPS-derived positions with traditional ground-based navigation aids and situational awareness. In the future; we will increase monitoring frequency when operating in areas protentially suseptible to GPS unreliability.