Continuity: When Agent Hoffman writes the letter to Amanda, he puts the envelope so her name is pointing down, yet when Amanda opens the drawer her name is at the top. The director had to do this or it would have revealed Hoffman was the new apprentice all along.

Continuity: The blood stain on Riggs' white shirt around the neck has blood under the collar, then at the end it is over the collar and has increased in amount.

Other: Lean says "Jeff" completely different to when she says it in Saw 3. When the door finally closes, she screams "Jeff!" for ages. Once Jigsaw's throat is cut in Saw 3, she stops.

Continuity: When Agent Strahm has finally realised where the final game is being played, he holds up the piece of paper of Jigsaw and Art outside the Gideon building. There is a hand at the top of the picture, which is a newspaper clipping, but he is holding a picture, not a newspaper. This is a reused shot of when he shows Agent Perez the picture earlier in the movie.

Revealing: When Riggs arrives at the shop, the clock shows 1:16. But, at a second look, it's 3:46.

Visible crew/equipment: As Jill is being interrogated, when it cuts to a shot where the two cops are looking at her through two way glass, a camera man is visible between them and the boom mic in seen at the top left hand corner, very faintly.

Visible crew/equipment: Several times in the movie you can see a stunt double for Donnie Wahlberg, like when he tries to hang himself. Art runs over and there is a wide shot focusing on both of them. No slo-mo required, but you can see it's a stunt double.

Continuity: When Rigg is talking to the little girl, he says, "How did you get those marks on your arm?" Later, in his flashback, he says, "How did you get those marks on your hand?"

Continuity: If you go back and compare the ending of "Saw III" with the ending of "Saw IV", you can tell the lighting is different in certain areas (specifically when Strahm sees the dooor swing shut on its own), even though it is supposed to be in the same time and place.

Continuity: When Rig opens the door the clock says 00:00 time left, but when he is talking to Art on the floor the clock says 00:01.

Continuity: *SPOILER* When Agent Strahm breaks into the Jigsaw's room in the end, he literally comes in less than a minute after "Saw III"'s conclusion. Yet, if you look, Amanda's dead body is in a completely different position than the end of "Saw III", which makes no sense, as there was no time or reason for it to be moved. At the end of III, her body was facing towards Jigsaw, and there was only a small amount of blood around her. Here, her body is facing in a different direction, and there is a ridiculously larger amount of blood.