I crossed the Dartford crossing in June. I forgot to pay the charge until a couple of days later (I have the receipt). The same day they issued a penalty notice. When I received it I phoned and they said as I'd paid it was ok and they would squash the charge. Today I received another one saying as i haven't paid it's gone up to £105 plus the originally £2.50. I've phoned them but they say I have to pay £107.50 as the PCN had been issued, I needed use the PCN number when I paid late. So the charge I paid doesn't count. I can appeal but the person on the phone thinks it will be pointless as I'll lose. Do I have to pay?