After a random stop by the police, my son got his vehicle taken away for an overdue license plate. He knows forgetting to pay wasn’t smart, fortunately he works, thus the next day he took back possession of his vehicle.
In my opinion these are the type of unfortunate events that are good for children with tendency to “forget”. He’s a first year driver, thus what happened is sort of good because it is not harmful nor costly and served as real life lesson. Real life lessons go beyond the capability of verbal warnings parents give to children, to live it, is the ultimate lesson.
The wrong thing to do with children at the stage of adulthood is to have been there like a hawk and made sure he paid.