Penalty fare
What it really means
A fine (often £100, reduced if paid quickly) for travelling without a valid ticket. "I did not know" is not accepted as an excuse, so always buy a ticket or tap in before boarding.
Context, tips & common mistakes
The standard rail penalty is £100, reduced to £50 if you pay within 21 days, plus the fare owed — and it applies to honest mistakes, not just deliberate fare dodging: boarding with an expired railcard, sitting on the wrong operator's train with a restricted ticket, or travelling before an off-peak ticket becomes valid can all qualify. If you genuinely could not buy a ticket (broken machine, closed office, no working card reader), say so at the time and note the evidence, because there is a formal three-stage appeal process with an independent final stage — appeal in writing within the deadline printed on the notice rather than arguing on the platform. Do not ignore a penalty fare: unpaid notices can escalate to prosecution, and deliberate evasion can be prosecuted directly. On London services, TfL runs its own penalty system with similar logic. If staff stop you, stay polite and give correct details; giving a false name or address turns a fixable mistake into a criminal matter.