London Underground: tap in and tap out
Do
- Tap your Oyster card or bank card on the yellow reader both on entry and exit, even if the gates are open
- At interchange stations with mid-route readers, tap as instructed
Don’t
- Tapping in but not out, or not tapping before boarding
If you miss a tap you are charged the maximum fare; if an inspector finds you travelling without tapping, you may be fined or prosecuted.
Not yet verifiedSource: Wikipedia: Oyster card