In each NFL game, coaches are given two chances to challenge a ruling they disagree with, and reviews are automatically initiated by a replay official after any scoring play or turnover. However, there are a few plays that cannot be reviewed by officials even if the initial ruling on the field was, in fact, incorrect.
The NFL rulebook lists eight different situations that cannot draw a replay review, and it includes penalties. A replay cannot be used to determine whether or not a penalty should or shouldn't have been assessed, with the exception only of 12 men on the field or an illegal forward pass that can be changed after a review.
Replays cannot be used to review the status of the game clock, play clock or the down of the play, although a rule change in 2015 allows the officials to check if time in a half expired incorrectly and add time on the clock, if necessary.
The other five situations that cannot be reviewed are as follows:
- Runner ruled down by defensive contact or out of bounds (not involving fumbles or the line to gain)
- The position of the ball not relating to first down or goal line
- Field-goal or Try attempts that cross above either upright without touching anything
- Erroneous Whistle
- Quarterback "spike" to kill clock
Many debates about whether a play is reviewable or not are determined by if a hypothetical situation would be created with the replay.
For example, if an official blows his whistle to say that a player stepped out of bounds when running down the sideline, a replay couldn't be used to determine that the player stayed in because the remainder of the play never occurred after it was ruled dead by the whistle. Alternatively, if a player runs down the sideline for a touchdown, a replay can be used to rule that he stepped out of bounds during the play.
If a coach twice challenges a play and replay overturns the original call on the field, that coach will be awarded a third opportunity to challenge.