In the final fight, the blood on Brax's mouth disappears and reappears between shots, and glaringly switches from one cheek to another.
As Christian writes a goodbye note to Dana, he begins with a very large capital 'D' followed by the 'ana' at the widest part of the 'D'. As he finishes the note, the 'ana' is much lower, and near the bottom of the 'D'.
When Christian Wolff is having lunch with Dana, the cuffs of his shirtsleeves are unbuttoned when he is talking with her and when he is saying goodbye to her, they are buttoned.
Early, when Chris visits his camper at the garage rental place, he parks his truck over the word "STOP" -- his tires are on the letters. But, when he opens the garage door, his truck is parked well before the letters. Also, the truck casts much much less of a distinct shadow on the ground.
When Christian Wolff is having lunch outside living robotics he screws off the drinking cup of the thermos flask. He puts the cup on his right side of himself. In the next shot the cups on the left side of him.
The Department of the Treasury seal on the podium at press conferences list the date of the Department of the Treasury on the bottom of the seal as 1788. The Department of the Treasury was actually established on September 2, 1789.
At the funeral viewing, the Army uniforms are worn incorrectly. The shoulder epaulets should be under the lapel of the green army jacket.
When Christian is shooting the melons, his host states the distance to be 1 mile. Bullet flight time for a .50cal round over 1 mile is 2 seconds, yet the melons are shown to be hit almost instantly.
Dana tells Chris that she studied accounting at the University of Chicago. However, the University of Chicago does not have an undergraduate accounting program.
Dana states that she went to Harrah's Joliet to play blackjack for money to purchase a dress for her high school prom. The minimum age to gamble in the state of Illinois is 21.
Christian states that growing up he lived in 34 homes in 17 years. Dana asks, "You moved 34 times?" Christian answers in the affirmative. He only moved 33 times. As precise with numbers that might seem like an obvious error. However many autistic people tolerate inconsistencies and errors that neurotypical people make, as well as being able to identify and attempt to make sense of idioms and sayings.
The two people that Christian kills with his Barrett M82A1 .50 caliber rifle via head shots are only shown falling down with some blood splatter. In reality, bullets of that size would have completely blown their heads apart, as demonstrated earlier on in the movie when Christian is using cantaloupes as target practice for his Barrett on the Rices' farm.
When Sorkis was giving Marybeth information on the face recognition of The Accountant, he plays the recording of when Little Tony was killed, saying that the place was bugged. When Little Tony dies by getting kicked in the head, the audio file loses the signal and goes to static. Unless the bug was on the face of Little Tony, the signal would not have died.
After wandering around Christian Wolff's back garden where there is mud, grass and leaves on the ground, Ray King is in Christian's house. He sits down and puts his feet on a table where we can see that there is not a single speck of dirt on his boots. There is absolutely no wear on the treads of the boots suggesting that they are brand new and have never been worn before.
When Christian throws the whiteboard markers in the bin, he does that without the caps on, staining the bin. This is out of line with his character.
When Medina is looking in the FBI's Suspected Gambino Family Associates database, two of the photos are the same.
In the fight between Chris and the mercenary in which Chris armed a grenade and put it in the merc's vest, some have said that the grenade would have killed them both. The grenade was a flashbang type which would have been contained by the vest.
In a scene that takes place in 2003, a police car has an FS Arjent lightbar on it, which didn't exist back then.
When Chris, his brother and his father are in France in the 1990s, the car's wipers are aerotwin shaped. These shaped wipers were invented in 2000 at the earliest.
Dana tells Chris that she was an accounting major at the University of Chicago. However, the University of Chicago does not have an undergraduate business program and no accounting major.
When Christian Wolff is first sitting down with Rita Blackburn and Ed Chilton at the conference table in the all-glass room to discuss taking on the accounting job, you can clearly see Christian's reflection in the glass behind Ed Chilton. The man you see in the reflection is a stand-in, not Ben Affleck himself.
When Chris, his brother and his father are in France, in a Peugeot 505, the car shown is a US market version with dual round headlights. The European version had single trapezoidally shaped headlights.
A rich guy like Blackburn would totally have or invest in armored panic room, especially one who has his life threatened and is spending thousands of dollars hiring an army of heavily equipped mercenaries. Instead Blackburn nervously moves about openly annoying his bodyguard mercenaries because he is scared for his life. The writer never realized or purposely ignored a simple logical fact.
Ray King had retired/resigned when he receives a call with a tip-off. If he was walking out the door with his work possessions in a box, he wouldn't be able to pick up a new case.
When Agent Medina is looking up Lewis Carroll, the first screenshot shows he is an author of "The Hunting of the Snarl". This is corrected in a later screenshot of what seems to be the same page as "The Hunting of the Snark", the correct title of Carroll's work.
When the man remarks that Justine's computer is a BX32, it is actually a custom build using a corsair carbide air 540 case.
Between 1:49:15 and 1:51:41 Braxton and Wolff fight and argue because Braxton blames Wolff for the death of their father. Braxton tells Wolff that if he had needed to attend the funeral, Wolff should have called Braxton to back him up. In the funeral flashback (1:35:07-1:36:15), Wolff never comes near the casket. It is the father who seems most affected by the death, with Wolff either backing him up or attending on orders from a superior officer. Wolff never corrects Braxton with the truth; as an autistic it would be more in keeping for him to be honest about why the father was there, rather than taking the blame to shield their father's choice.
When Christian is meeting with Rita and Ed for the first time to discuss the accounting assignment, Ed gets pissed off by something Christian says. He turns to Rita and expressing his frustration calls her "Dana"(Dana is Anna Kendrick's character).
On a sign in the Living Robotics building, "cutting-edge" is spelled without the hyphen.