Each time the Chicago Metra train pulled into Union Station, the PA announcer kept saying that it was the end of the red line. The CTA (Chicago Transit Authority) uses color coded routes, and the Metra system uses actual named routes (Metra Milwaukee District North). Also, the view of the train entering the city shows it entering from the south, but Charles' briefcase tag says he lives in Wilmette which is north of the city.
When Lucinda and Charles are looking for a hotel the first hotel that Charles asks about is The Renaissance Hotel which is on Wacker Drive. Later when Lucinda asks the taxi driver to stop the cab the cab is again in front of The Renaissance going the opposite direction on Wacker. However, when the cab comes to a stop and they get out of the cab they are not standing out on Wacker Drive, nor in front of the Renaissance.
The Rock Island route on Metra is colored red in the system map and it services as far south as Joliet. Lucinda mentions living in Lake Forest which is north of Chicago and serviced by UP-N (Green) line.
At the end of the movie, Charlie retrieves this brief case and you are led to believe he gets his money back. The brief case is black, which was the one he gave them with $10K in it. The one with $100K was older and different, it was brown which implies he didn't get the $100K back.
After firing his P228 a couple of times, killing the new scam victim, La Roche attempts to shoot Schine. His pistol (which is clearly in battery) goes "click", upon which he is seen inserting a new magazine and then pointing the gun again at Schine, who shoots him before he can get a shot off. What no one one the set seems to have realized is that an empty pistol a) does not go back into battery, b) cannot go "click", and that c) as long as you don't rack the slide or the bolt of a gun that went "click" the probability of it firing on the next trigger pull is pretty exactly zero percent (La Roche's 228, being a SA/DA-gun, would have went "click" again had Vincent Cassel pulled the trigger).
The goof items below may give away important plot points.
(Possibly deliberate error by the filmmakers.) At the opening of the film, a character is writing in a blue notebook (the words are voiced by Clive Owen.) When this character lights the cigarette in his mouth, he is clean-shaven. At the end this character is revealed to be LaRoche, but he has had facial hair throughout the entire movie.
After LaRoche shoots Winston in the car in the back of his head, his head hits the steering wheel. When Charles moves Winston's head backward, his face is filled with blood. In a later shot of the front of the car, with Winston's face facing the side window, there's no blood at all.