If a game is tied at the end of four quarters, overtime is played. During the regular season in the NFL, one overtime period is played (with each team receiving two time outs), and each team receives one possession to score, unless one of them scores a touchdown on its first possession. Sudden death rules apply if both teams have had their initial possession and the game remains tied. If both teams are tied after the 15-minute overtime, the game officially ends in a tie. Overtime follows a three-minute intermission after the end of the regulation game. Prior to start of overtime, a coin flip is performed where the captain of the visiting team calls the toss. The team that wins the coin flip has the option to either receive the kickoff or choose the side of the field they wish to defend. Ties are rare in the NFL; the game between St. Louis and San Francisco on November 11, 2012 ended in a 24-all tie, the first tie since 2008.
Beginning in the 2010 NFL post-season, a modified sudden-death system for overtime games was put into effect. The overtime rules were changed to reduce the apparent advantage gained by the team that won the overtime coin toss. Under the prior rules, the team that won the coin toss would usually elect to receive the ball, then gain just enough yardage to win the game by kicking a field goal without the other team ever touching the ball. The modified rules allow both teams to have the "opportunity-to-possess," with one exception. The exception occurs if Team(A) scores a touchdown (not just a field goal) on their initial possession in overtime, then the game is over and Team(A) wins. But if a touchdown is not scored on Team(A)'s opening drive, or if they score only a field goal, then Team(B) is given an opportunity to possess the ball by either a punt, a kick, or by taking over on downs from Team(A). Of course, Team(B) could also gain possession by an interception or fumble from Team(A). Once the requirement for "opportunity-to-possess" has been satisfied by both teams then normal sudden-death rules apply, meaning that the next team to gain more points than the other team wins the game (note that it's possible for a tie score to occur during overtime play under these rules). Various events may occur that constitute "opportunity-to-possess" even though a team may not gain full possession of the ball in order to run a play. For example, if Team(B) muffs a kickoff or punt return (i.e., drops the ball while attempting to catch it) which is then recovered by the kicking Team(A), then Team(B) is considered to have had their "opportunity-to-possess," and normal sudden-death rules would then be in effect. Similar to normal overtime, following a three-minute intermission after the end of the regulation game, a coin flip is performed wherein the captain of the visiting team calls the toss. However, in post-season overtime, multiple 15-minute overtime periods may be played until a winner is declared. The first post-season overtime game played under the new overtime rules occurred in the 2011-2012 NFL AFC Wildcard Playoff game between the Denver Broncos and Pittsburgh Steelers at Sports Authority Field at Mile High, Denver, Colorado. Denver won the game on the first play in overtime, an 80-yard touchdown pass from Tim Tebow to Demaryius Thomas.
NFL Europa, a defunct league run by the NFL, used a 10-minute overtime period, with the constraint that each team must have the opportunity of possession; once both teams have had such an opportunity, the overtime proceeds in a manner similar to the NFL's. Thus, if Team A has the first possession of overtime and scores a touchdown and converts their kick (thus being 7 points ahead of Team B), Team A would then kick off to Team B (In the NFL, the game would have ended with the touchdown, without a conversion being attempted). Team B would have to match or exceed the 7 point difference within this ensuing possession; exceeding it would end the game immediately, while matching the difference would result in a kickoff to Team A. From this point, the overtime is sudden death. The new United Football League also uses this rule.
The defunct World Football League, in its first season of 1974, used an overtime system more analogous to the system long used in international soccer. The overtime consisted of one 15-minute period, which was played in its entirety and divided into two halves of 7½ minutes each, with each half starting with a kickoff by one of the teams. The league changed to the NFL's sudden-death format for its second and last season in 1975.
In college and high school football, an overtime procedure (the Kansas plan) ensures that each team has equal opportunity to score. In college, both teams are granted possession of the ball at their opponents' 25 yard-line in succession. A coin flip takes place, with the winning team having the option either 1) to declare that they will take the ball first or second, or 2) to decide on which end of the field the series will occur (both teams' series occur on the same end of the field). The losing team will have the first option in any subsequent even-numbered overtime. In the first overtime, the team with first series attempts to score either a touchdown or a field goal; their possession ends when either a touchdown or a field goal have been scored, they turn the ball over via a fumble or an interception, or they fail to gain a first down. After a touchdown, a team may attempt either an extra-point or a two-point conversion. However, if the team on defense during the first series recovers a fumble and returns it for a touchdown, or returns an interception for a touchdown, the defensive team wins the game. (This is the only way for a college overtime game to end without both teams having possession.) Otherwise, regardless of the outcome of the first team's series (be it touchdown, field goal, or turnover), the other team begins their series. If the score remains tied after both teams have completed a series, a second overtime begins. If the score remains tied after two overtimes, teams scoring touchdowns are required to attempt a two-point conversion from the third overtime on. Just as in regulation, if a defensive team recovers a fumble/returns an interception to the end zone during a two-point conversion attempt, they will receive two points.
In high school football in a majority of states, each team is granted possession of the ball at the 10-yard line, meaning that a team cannot make a first down without scoring except via a defensive penalty that carries an automatic first down (such as defensive pass interference or roughing the passer). As is the case with the college overtime rule, the team that wins the coin toss will have the choice as to whether to take the ball first or second, or decide at which end of the field the overtime will be played. The other major difference between overtime in college football and high school football is that in high school football, if the defense forces a turnover, they may not score. However, in Texas, the college overtime rule is used, as both the University Interscholastic League, which governs interscholastic activities for Texas public high schools, and the Texas Association of Private and Parochial Schools, the largest analogous body for Texas private high schools, play by NCAA football rules with a few modifications for the high school level.
The defunct XFL used a modified Kansas Plan which, upon the first team scoring, required the opponent to score the same or greater amount of points in the same or fewer downs (i.e. if the first team scored a touchdown, and converted the one-point conversion in three downs, the opponent would have to match that touchdown and conversion in three downs as well). Each team started at the 20-yard line, but like high school, there were no opportunities for first downs. The league also banned field goals except for on a fourth down.
Read more about this topic: American Football Rules, Time of Play