Heading to Paris soon. I am confused about "composting" RER and Metro tickets. Can somebody explain? Merci.

It's a little (yellow? I think) box on the platforms where you board. You need to "punch" ("composter&quot your ticket, showing the time you're planning to use it. Many tickets are sold that could be used today, tomorrow, next week. If youhave one that hasn't been punched, while you are on board, it is as good as indicating that you would be trying to re-use it, over and over again.

Best wishes,

Rex

Rex's description is correct; HOWEVER, you don't composte métro and RER tickets!!! It's just for train (SNCF) tickets. On the métro and RER you just stick your ticket in at the turnstile, keep the ticket with you all the way to the end, and get off.

But the Metro ticket can be used in a bus, where you must validate it.

In my experience, the rider is required to insert the ticket into a little machine that imprints it with the date and time.

Similar little boxes are located in rail stations for the same purpose.

If you have a pass, I presume you show it when asked. If you don't have a stamped ticket in your possession, and an inspector comes on to check tickets, you will be in for a bit of a hassle.

I never experienced a "control", but I have heard that a fine is imposed on violators.

One of my "rookie traveler" mistakes was not stamping my ticket on a bus. I didn't know the rules, but that didn't matter. The conductor came around to check tickets. When he saw mine wasn't stamped, he gave me a citation and I had to pay on the spot. In those days the fine only translated to about $8 US, but it was quite humiliating.