In the classic Monopoly board game, a player pays $50 to leave Jail immediately.
A player may pay this amount before rolling, then leave Jail and move normally on the next roll. Alternatively, the player can try to roll doubles on one of the next three turns, or use a Get Out of Jail Free card. If doubles are not rolled by the third attempt, the $50 payment is required before moving according to that roll.
The payment is separate from any rent, tax, or purchase made after leaving Jail. A common mix-up is confusing the $50 Jail payment with the $50 value printed on some property-related calculations or with the original $200 salary for passing GO.
Jail also functions as a regular board space when reached by an ordinary move. Only a player sent there by the Go to Jail space, a card, or the three-doubles rule is actually in Jail.