Nick shaves, but in the next scene he has stubble.
When Grace gets shot, the bullet strikes her upper bicep. In the next scene, the wound is much higher, in mid-shoulder.
When Audrey hits Nick in the library, she strikes his left eye. Immediately after the hit his hands are in his left eye, but in the next scene his hands are covering his right eye.
During the Monaco Grand Prix, one of the on-board vehicle shots shows Juan Carlos (in the orange car) starting the race in 3rd. However, a later shot of the first corner of the race shows that he has not overtaken anyone, and that he is actually7th.
When Nick and Audrey are chasing Juan Carlos they are about to plow into a goat. However the orientation of how the goat is standing changes from one cut to the other.
There are three ranks of detective in NYPD. The first two levels are decisive by the police commisioner, Detective Grade 3 and Grade 2; Grade 1 is a civil service test. Further Nick is a sergeant; this out ranks a detective so it is unnecessary for him to take the detective test. All police officers are trained with investigations.
After the murder, Nick tells the Captain to call Interpol. Contrary to what is often depicted, Interpol is not an actual police force. It is a liaison association comprised of police officers in member countries so as to assist in fighting crime that crosses international borders and extradition of criminals. In the US for example, the Interpol liaison agency is the FBI.
While on the yacht heading to Monaco, Juan Carlos Rivera is congratulated for "racing in the Monaco Grand Prix tomorrow." All drivers are required to be at Monaco no later than the Wednesday before a race on Sunday. There are two practice sessions on the Thursday and a short practice session followed by a qualifying race on the Saturday.
The French detective tells Nick they had made an inquiry on him, and mentions him failing the detective exam several times. The NYPD would not release employee information such as this to an outside agency, only that he was employed as an officer.
When Jennifer Aniston is working on a client in the salon she applies color between the foils without wearing gloves and a real hairstylist would know this is illegal and dangerous.
When Juan Carlos threatens the detective that is in the car with him, the gun he holds has no magazine in it.
At one point in the film it is said that Nick is a Sergeant in the NYPD. The Sergeant badge in the NYPD is a larger, brass/gold shield with an eagle on top. Throughout the movie, the badge Nick flashes around is a nickel/silver badge worn by the lowest rank of police officer who have not been promoted to detective or higher, which Sergeant is.
FOURTH WALL BREAK: In the salon when Lorraine (Jennifer Aniston's character's customer) mentions the "Employees Must Wash Their Hands" signs in restaurants, she looks directly at the camera as she says the sign is really for men.
Colonel Ulenga is wearing a charlie foxtrot of modern, American ribbons, combat and non-combat, and they're not even in the proper precedence. They include the Silver Star, Purple Heart, USMC Good Conduct, the Navy and Marine medal, and Desert Shield/Storm, to name a few. Not one award from the UK or Europe.
When Nick and Audrey are introduced to the Maharaja, the straw in Nick's plastic cup is obviously inserted incorrectly.
When Charles picks up Audrey right after she had a fight with Nick, they're all still in Monaco, but if you pause the movie right when the car pulls away, you will see that that scene was actually shot in Milan: You can see the classic "M" of Milan's metro and on the right is a road sign that says "Area Pedonale" in clear Italian.
At 1 hour into the movie, when Nick buys the prepaid phones (supposedly in France), the text on the boxes is in English and the visible price tag in USD.
The plane is said to be landing in Malaga - Spain. However it is obvious that the landscape is Italy.
French inheritance law doesn't state that the estate is divided amongst the children, if the person is married. In that case the spouse's part of the estate is divided thus: ¾ to the children and ¼ to the spouse. So if a couple had $1,000,000 and they shared it equally, the deceased's estate would be $500,000 and the children would share ¾ of that.
It means that the real motive would be to stop a wedding rather than the signing of any will: if someone dies with no spouse then the entire estate goes equally to the children.
While chasing the police car, Nick tells Audrey she has to "pit" him. Pit stands for pursuit intervention technique, and is performed not by ramming the rear bumper as he stated but instead by pulling alongside and steering into the rear fender.
Audrey shows Grace Ballard's Wikipedia article to Nick, pointing out that her last name isn't actually "Ballard". However, the article synopsis briefly displayed on Audrey's phone clearly shows her full name as "Grace Madeleine Ballard."