En Prison

En Prison is a European roulette rule that, when the ball lands on zero, locks your even-money bet "in prison" for one more spin instead of taking it immediately, giving the stake a chance to be returned. It applies only to even-money wagers such as red/black, odd/even and high/low, and it exists purely to soften the cost of the zero pocket. When zero hits, the imprisoned bet is not settled. It stays on its original selection through the next spin. If that selection then wins, you get your original stake back but no winnings; if it loses (or another zero appears), the stake is forfeited. This single second chance is what lowers the house edge. Worked example: you stake £10 on red on a single-zero wheel. The ball lands on zero, so your £10 is imprisoned rather than lost. On the next spin, red wins, and you receive your £10 back with nothing extra. Across many rounds, En Prison effectively returns half the value of even-money bets that hit zero, cutting the house edge on those bets from the standard European 2.70% to roughly 1.35% - one of the best odds available in a casino. Why it matters: not every roulette table offers this rule, and it applies only to even-money bets, so a straight-up bet on a single number still carries the full 2.70% edge. The common mistake is assuming En Prison and la partage are identical. La partage returns half the stake instantly on a zero, while En Prison holds the whole stake for one more spin. Both reach a 1.35% edge, but the mechanics differ. Compare with la partage, even money, roulette and house edge.