Does anyone here have any knowledge of regulations regarding cabs in Paris?

I was a bit perturbed yesterday when the meter on a cab I took between
two railway termini read only E-Erreur. I suspect the driver had
switched off the meter and was on the fiddle somehow. We were not
overcharged for the trip (I suspect the driver understood I was
suspicious as I told my partner in clear English that I thought
off-meter work was illegal).

I have noted the cab's number.

My French is rather poor but I wonder if I should still try to report
the matter somewhere.

--
Helen D. Vecht:
Edgware.