While watching the pre-game for the 2015 Women's World Cup final, they said that Japan would be using a 4-3-3 formation. Why did Japan give up that strategic information? Wouldn't it be better to keep it secret so that the USA couldn't use that information to devise counter strategy? I can't imagine they are required to submit a formation ahead of time, because it is such an abstract thing.
As Phab mentioned, teams do not have to give any indication of their formation. They only need to provide a list of 11 players who will take the field at the start. The broadcasting companies take an educated guess, with the help of pundits and experts, as to the formation of the team and positions of the players. They are right most of the time but could be completely wrong as well.
According to the regulation for the Women World Cup (page 35):
Each team is responsible for arriving at the stadium at the latest 90 minutes before the kick-off of the respective match and for providing the completed start list to the FIFA General Coordinator upon such arrival.
Each team is responsible for ensuring that the start list is completed properly and submitted on time, and that only the selected players start the match. In the case of any discrepancies, the matter will be submitted to the FIFA Disciplinary Committee.
There are additional details in case a starting player get injured during the warm-up.
With the list of 11 starting players and knowledge of previous games, it is possible to infer the formation (4-3-3; 4-4-2 or any other) although surprises could be prepared.