Fastpitch Rules USSSA
You asked
What happens if we accidentally use an ineligible courtesy runner?
?Depends
Ineligible courtesy runner is out if caught early
If she's still on base when it's discovered, she's called out and your team gets a warning — but if it's the first time, no ejection. A second offense in the game gets the head coach ejected for the rest of the game. Timing matters though — the moment she actually swaps in for the pitcher/catcher on that base and the ball goes live, that's when the clock starts on catching the mistake (Rule 8 Sec 3.B).
USSSA · RULE 8 Sec 3.C-G 2026 edition
See the rule text (8)
USSSA · RULE 8 Sec 3.C-G

C. A runner put in for any player other than the pitcher or catcher is considered a substitute player. D. A player may not run as a courtesy runner and also be used as a substitute for another player in that half inning. EXCEPTION: if there is an injury and no substitute is available, the courtesy runner must be used as the substitute and take the injured player's place; if the courtesy runner was on base, the pitcher/catcher for whom she was running must run in her place. E. Once a courtesy runner is designated for a half inning, no other courtesy runner or the pitcher/catcher may return to run for the original courtesy runner (unless injury occurs, in which case another courtesy runner or the pitcher/catcher may run until scoring or being put out). F. The courtesy runner may not be used for the DP unless the DP is the pitcher or catcher of record. G. In the top of the first inning only, the pitcher and catcher are those listed on the lineup card, and both must face at least the first batter on defense (one pitch); thereafter they are identified as the last players who physically played that position on defense. The pitcher/catcher must reach base legally by means other than substitution to be eligible for a courtesy runner. EXCEPTION: if injury/disqualification occurs to the lineup-carded pitcher/catcher in the top of the first before she faces the first batter in the bottom of the first, the player who ran for her is retroactively her substitute (unless an LCAB courtesy runner), no longer a courtesy runner, and the pitcher/catcher has left the game and may not return to that position. PENALTY for unreported courtesy runner: treated the same as an unreported substitute — team warning, with further violations resulting in coach ejection.

USSSA · RULE 8 Sec 3.A-B

A. The team at bat may use a courtesy runner for the pitcher and/or catcher any time after they reach base other than by substitution. The same runner may not be used for both positions in the same inning; neither the pitcher nor catcher is required to leave under such circumstances. B. Players who have participated in the game in any other capacity are not entitled to serve as a courtesy runner (must be an unused substitute). (Non-Elite Select divisions): if, and only if, no eligible substitute is available, the Last Completed at Bat (LCAB) may serve as a courtesy runner, subject to other restrictions. NOTE: if an eligible substitute is present but unable to run due to injury/illness, that player is ineligible for the entire game if the team uses the LCAB option. The LCAB courtesy runner is determined when requested, skipping batters (1) currently on base, (2) who are the pitcher/catcher of record, or (3) who already courtesy ran for the other position that inning. In the first inning, if no substitutes are available, the LCAB courtesy runner is the person furthest away in the batting order (the last listed batter, for the lead-off batter). PENALTY: an ineligible/incorrect courtesy runner discovered while still on base is called out and a team warning issued; second offense ejects the head coach for the rest of the game. Liability for discovery attaches once the runner physically replaces the pitcher/catcher on the occupied base and the ball becomes live.

USSSA · RULE 8 Sec 18.I

A runner is out when prevented from being put out by an illegal act by anyone connected with the team. NOTE 1: if, in the Umpire's judgment, this interference attempts to prevent a double play and occurs before the runner is out, the immediate trailing runner is also called out. NOTE 2: if a retired runner interferes and another runner could have been put out, the Umpire declares the runner closest to home out. NOTE 3: if the batter-runner interferes, the Umpire calls out the batter-runner and the runner who has advanced nearest home. NOTE 4: if two fielders try to field a batted ball and the runner contacts one or both, the Umpire decides which fielder is entitled to field it, and only that fielder is protected. NOTE 5: if a batted ball is misplayed but the fielder is still making an initial play and the runner contacts the fielder, it is interference; if the misplayed ball bounds away so it is no longer within a step and reach, and contact then occurs, it is obstruction.

USSSA · RULE 8 Sec 18.Y-AC

The runner is also out because of other team members' actions: Y. a runner on base leaves the game without an eligible substitute available (EXCEPTION: an injured runner departing per Rule 5-2-A-1). Z. anyone other than another runner physically assists her during playing action. AA. a coach intentionally interferes with a live batted or thrown ball. AB. the offensive team causes a blocked ball (EFFECT: the runner closest to home is out; if no play is obvious, no one is out, but all runners return to the last base touched when the ball became dead). AC. a coach runs in the direction of home plate or any other base, on or near a baseline, while a fielder is attempting a play on a batted or thrown ball, thereby drawing a throw in that direction.

USSSA · RULE 8 Sec 8-9

Sec 8. A runner becomes liable to be put out when: (A) with the ball in play or on awarded bases, failing to touch a base before attempting the next; (B) after overrunning first base, attempting to continue to second; (C) after dislodging a base, attempting to continue to the next base. Sec 9. If a batter-runner is entitled to return to first after overrunning, or a runner fails to touch home plate, and wishes to return, the runner shall return immediately.

USSSA · RULE 8 Sec 6.G-K

G. Two runners may not occupy the same base simultaneously; the runner who first legally occupied it is entitled to it unless forced to advance, and the other may be put out by being touched with the ball. H. A preceding runner's failure to touch a base or legally tag up (and being declared out) does not affect a succeeding runner who touches bases in proper order — but if that failure is the third out of the inning, no succeeding runner may score. I. No runner may return to touch a missed base or one left too soon after a following runner has scored or once the runner leaves the field of play. J. Bases left too soon on a caught fly ball must be retouched before advancing to awarded bases. K. Awarded bases must be touched in legal order.

USSSA · RULE 8 Sec 16

A runner must return to base when: (A) a batted ball is foul; (B) an illegally batted ball is declared; (C) a batter, batter-runner, or runner is called out for interference (other runners return to the last base legally touched at the time of interference); (D) any part of the batter's person/clothing is touched by a pitched ball swung at and missed; (E) a batter is hit by a pitch, unless forced; (F) an intentionally dropped ball is ruled. EFFECT for A-F: the ball is dead and each runner returns to their base without liability, except when forced to the next base because the batter became a batter-runner. G. When the Plate Umpire interferes with the catcher's attempt to throw out a stealing runner, or an attempted pick-off: EFFECT: delayed dead ball. If the runner is ruled out, the ball remains live; if not out, all runners return to the base occupied at the time of the pitch. It is not umpire interference if, on a passed ball or wild pitch, the umpire is hit by a catcher's throw — the ball remains live.

USSSA · RULE 15 Sec 12 Notes and Sec 13-14

NOTE 1: while runners may advance and return until time is called, their activities are governed by Rule 8, Section 2 (the Look-Back Rule) if the ball is returned or possessed by the player-pitcher in the pitching circle; all references to "pitcher" in Rule 8, Section 2 apply to the "player-pitcher" in Coach-Pitch. NOTE 2: for awards based on runner positioning relative to the halfway line, if a runner is obstructed and the obstruction hindered her ability to advance past the halfway point, the umpire may award the next base to compensate for the defensive violation. 13. Conferences: a. the offense may have one charged conference per inning per Rule 4, Section 8.B. b. the defense may have three charged conferences in a seven-inning game, and only one per inning in any Tiebreaker inning, per Rule 8, Section 3.A. PENALTY: for excess defensive conferences, the player-pitcher is removed as player-pitcher for the remainder of the game. 14. Additional Coaches: besides the two base coaches, the only other coach permitted on the field is the Coach-Pitcher, who must deliver the pitch with one foot in contact with the pitching plate and may only coach the batter prior to the pitch (not the batter/runner or baserunners at any time). PENALTY: the ball remains live until the play is over; first offense is a team warning, second offense results in a dead ball and the applicable runner out, subsequent offenses add restriction of the Coach-Pitcher to the dugout for the remainder of the game.

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