PCN code RUC-DART: use of a vehicle on a road in the charging area to which the Dart Charge (Dartford-Thurrock River Crossing) scheme applies
What this contravention code means, and how to appeal it · Road User Charging
Code RUC-DART means the council or TfL recorded your vehicle as use of a vehicle on a road in the charging area to which the Dart Charge (Dartford-Thurrock River Crossing) scheme applies, without payment of the appropriate charge. If you paid but it wasn't recorded, or you believe your vehicle was exempt, that's worth challenging.
Full description on the ticket: “Use of a vehicle on a road in the charging area to which the Dart Charge (Dartford-Thurrock River Crossing) scheme applies, without payment of the appropriate charge.”
Can I appeal this?
Yes. This is a statutory Penalty Charge Notice from a council or TfL, not a private charge, so you have a formal right to challenge it before it escalates into a Charge Certificate.