On most TGV routes it is required that you validate your ticket, prior to travel by placing your ticket in the grey mouth-like slot near the bottom of the machine. It allows you to insert one end of the ticket (length wise), use the left end of the ticket, where there is usually a bar code and an SNCF logo.

In 2026, the requirement to validate (or "composter") your train ticket in France depends on the type of ticket you hold. If you have a physical paper ticket purchased from a station for a regional TER train, you must still insert it into the yellow validation machines on the platform before boarding to "stamp" it with the time and date. Failure to do so can result in a fine of up to €50. However, for TGV InOui and Ouigo (high-speed) trains, your ticket is already linked to a specific seat and time, so no physical validation is necessary. Most importantly, if you use an E-Ticket or a QR code on the SNCF Connect app, you do not need to use the platform machines at all, as the conductor will simply scan your digital code. The traditional yellow "composteur" machines are being phased out as the network moves toward a fully digital system.