Continuity mistake: When Charlotte Gainsborough has a meltdown telling the younger kid to remove the toy guitar, the kid is holding the toy differently between shots. (00:17:20)
Factual error: When the Senator is looking at the rent ledger, there are entries for each property as well as the date that money was collected. One of the dates is 2/29/74, yet 1974 was not a leap year. The only leap years in that decade were 1972 and 1976. (00:56:30)
Continuity mistake: When Young Jack threatens to throw his daughter out of the window, Young Madelyn promises him that she won't leave him. Pepper Binkley's hair is behind her left shoulder throughout the scene, except in the shot afterwards, when it's in front of the shoulder. (00:03:30)
Deliberate mistake: The (fake) confession letter was postmarked from Ohio and sent to Allison Connor, 331 Henry Lane in Hilliard, MB 21243. No U.S. state has a postal abbreviation of "MB." The way the "B" was written in thick bold letters made it resemble a "D" - "MD" represents Maryland (where the film apparently takes place). Also, there is no current 21243 zip code in the U.S. There is a 21241 for Baltimore City and the next consecutive zip code is 21244 in Baltimore County. The created address LOOKS real. (00:50:44)
Factual error: The movie is set in 1979-1980. You can see vehicles all throughout the movie that were manufactured after 1980.
Factual error: In golf scene, Kevin Spacey is supposed to be playing golf in St. Andrews. The intensity of sun and the surrounding fauna suggests they are actually playing on a course in the mid latitudes of the US. (00:11:30)