Posterior.
OBR 6.02(a)

Balk

A balk is an illegal act by the pitcher with runners on base — an attempt to deceive the runners, or one of thirteen enumerated violations like failing to come to a full stop from the set position. The ball is dead immediately and every runner advances one base.

Key points
  • Only possible with runners on base. With the bases empty, the same acts are illegal pitches and simply add a ball to the count.
  • Classic triggers: not coming to a complete stop in the set, throwing to a base without stepping toward it, dropping the ball while on the rubber, or starting a pitch and not completing it.
  • The penalty is automatic: ball dead, each runner moves up one base. A balk can score a run from third.
  • Umpire judgment is final — balks cannot be reviewed by replay.
In a game

Runner on first, pitcher flinches his shoulders in the set and the runner breaks for second.

Ruling · Balk if the umpire judges the flinch a start of the pitching motion. The runner is awarded second — not a stolen base.

Pitcher spins and throws to second where nobody is covering.

Ruling · Throwing to an unoccupied base without a legitimate play is a balk.

Why it moves the scoreboard

Each runner advances one base, so a balk can directly put a run on the board. It scores as a run like any other for the team and game totals.

Related rules