The United States takes on Japan in the World Cup final on Sunday, and there's a chance that there might not be a winner after regular time. If the match ends tied after 90 minutes, they'll have to play some extra time periods, and perhaps even go to penalty kicks -- like they did when they met in the last World Cup final.
During the Group Stage of the women's World Cup, games are allowed to end in a tie, each team is given one point, and they move on to the next match. But the 'Knockout Stages' of the World Cup are referred to as such for a reason -- there are no more ties. From the Round of 16 onward, until the final, each game will need to have a winner so that someone can move on to the next round, or lift the World Cup.
If a match is tied after 90 minutes, the two teams will play 30 minutes of extra time, separated into two 15-minute periods. In both periods, stoppage time will be calculated and added on, just like it is during the first and second halves. If the two teams are still tied after those 30 minutes, the tie will be settled by penalty kicks.
There is no 'golden goal', meaning the first goal does not win the match in extra time. Play will continue for the entirety of the 30 minutes of extra time no matter how many goals are scored, so if a team is scored on early, they have plenty of time to score again and force penalties, or score twice and win the game.
Penalties are best of five, and completed when one team is no longer mathematically able to beat the other in five rounds of penalties. If the teams are tied after five rounds, they go to sudden death, where each team takes a penalty until one team scores and the other misses in the same round.