Good question. I was taught to anticipate turns and my Garmin 430 will anticipate turns so that you do not overfly the fix. But I don’t remember any specific guidance on the matter, so I looked it up. I found this in the AIM.
5−3−5. Airway or Route Course Changes
a. Pilots of aircraft are required to adhere to airways or routes
being flown. Special attention must be given to this requirement
during course changes. Each course change consists of variables that
make the technique applicable in each case a matter only the pilot can
resolve. Some variables which must be considered are turn radius, wind
effect, airspeed, degree of turn, and cockpit instrumentation. An
early turn, as illustrated below, is one method of adhering to airways
or routes. The use of any available cockpit instrumentation, such as
Distance Measuring Equipment, may be used by the pilot to lead the
turn when making course changes. This is consistent with the intent of
14 CFR Section 91.181, which requires pilots to operate along the
centerline of an airway and along the direct course between
navigational aids or fixes.
b. Turns which begin at or after fix passage may exceed airway or
route boundaries. FIG 5−3−1 contains an example flight track depicting
this, together with an example of an early turn.
c. Without such actions as leading a turn, aircraft operating in
excess of 290 knots true air speed (TAS) can exceed the normal airway
or route boundaries… Consequently, the FAA expects pilots to lead
turns and take other actions they consider necessary during course
changes to adhere as closely as possible to the airways or route being