A fly that lands right or left of the target is not automatically a tracking error. A lateral miss can come from aim, tracking, line alignment, wind or turnover, so check them in order before changing anything.

• Aim and alignment. The 180 Degree Principle asks for the fly line and rod tip path to be aligned with the target at the start of each stroke, laterally and vertically; line swung out to one side gives a curved fly leg. Pointing the reel at the target is a useful teaching cue, not a complete diagnosis.
• Tracking. Tracking is the lateral path of the rod tip during the stroke. Twisting the wrist, or rotating the shoulder or body, curves it, and the fly leg curves with it; a fly leg curving right or left mirrors a curved tip path.
• Turnover. An unsuitable amount of delivery energy can make the line, leader and fly kick left or right as the cast finishes, especially sidearm, even when the tip path was straight.
• Wind. A cross-wind pushes the fly after it leaves the loop, so a miss that changes with the wind is not a tracking fault.
• Drill it. Targets tell you whether you were too far left or too far right, and tracking errors are fatal at the 30 and 45 ft targets. Cast at 45° above a tape measure: a straight tip path lands the line alongside the tape, not feet away.

Source

From the tracking faults and target work in the CI Study Guide (2025) (PDF) and the Horizontal Casting Drill in Appendix A; terms from the FFI Fly Casting Definitions (Tracking, 180 Degree Principle). See also Task 12, accuracy on-side and Task 13, accuracy off-side.