The violation reportedly took place during Week 6 when Washington traveled to face the New York Giants.
Haskins was penalized $4,833, a source told Schefter. Under the collective bargaining agreement, the club could have fined him up to $14,650.
The 15th overall pick in 2019 lost his starting job after struggling through the first four games of the season. In 13 career appearances, the Ohio State product has completed 59.6% of his pass attempts for 2,304 yards with 11 touchdowns and 10 interceptions.
Washington will carry a 1-5 record into Week 7, when the team meets the Dallas Cowboys.