More than 100 cars were stopped in the county by police cameras for having faulty number plates.
The 101 vehicles detected by automatic number plate recognition (ANPR) cameras across Hertfordshire made up around a third of those detected across the whole of the eastern region.
Operation Dragon took place across six counties between July 16 and August 5.
Illegal number plates include those which have fixtures which hide characters or alter spaces, use offensive language or don’t use the correct Charles Wright font.