Light Transport; Low Wing; 2 Turbojet Eng
Flight Crew Air Transport Pilot (ATP)
Communication Breakdown; Confusion; Human-Machine Interface; Situational Awareness
Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued New Clearance; Flight Crew Returned To Clearance
Human Factors; Airspace Structure; Chart Or Publication; Procedure
During getting clearance we were given a waypoint; EXTOL; which sounds very familiar to a close by waypoint EXALL. Waypoint was not originally on flight plan; and after finding what I thought was the correct waypoint I read [back] my clearance with EXALL. Both points sound familiar; I don't believe anyone noticed. During cruise we started making a turn to EXALL; when ATC inquired what fix we were going to. We verified the spelling and were informed to proceed to EXTOL.Flight path was corrected very quickly after initial diversion; and no further flight interruptions happened. Reading back exact spellings of every fix. EXTOL AND EXALL are in proximity and sound familiar. Although EXALL wasn't as good of a route as EXTOL; it wasn't unusual enough to raise suspicion.
Light Jet First Officer reported of confusion and questioning by Toronto ATC about their heading. Pilot programmed EXALL rather than EXTOL which led to a heading deviation.