Factual error: When Ewan McGregor drives to Belmont MA to visit Paul Emmett, he checks the mailbox to see whose mail it's addressed to. It shows the name Paul Emmett, address, Belmont MA 02324, which is the wrong zip code; it is the zipcode for Bridgewater MA, and Belmont MA should be 02478.
Continuity mistake: When the Ghost writer stops the BMW to follow the sat nav there is a car in the background. It vanishes then reappears as the film changes from close up to panoramic shots.
Factual error: Lang refers to 'The Times of London'. A British person talking to other British people, as he is, would always refer to Britain's premier newspaper by its correct title 'The Times'. Only foreigners call it 'The Times of London' to distinguish it from, for example, 'The New York Times' or 'The Times of India'.
Continuity mistake: When driving to the house for the first time, the taxi stops at the gates for a security check and Ewan is sitting in the back seat on the left (he passes his passport out the left window). In the next shot, as the taxi pulls to a stop at the house, Ewan is sitting on the right with his bag still in the middle of the seat. I doubt he switched sides for the short haul up the driveway.
Audio problem: When the news helicopter descends on the house as the news of the ICC trial breaks on the TV, the helicopter rotor makes no sound or almost no sound until the shot changes to see it, despite it being very loud once it is visible. The sound of its blades also fades very quickly as it leaves, despite any pilot presumably being very careful so close to a building.