TURN BACKS -- Referees are expected to honor their commitment to an accepted assignment. Occasionally there are valid reasons for not being able to honor an assignment, usually involving illness, family emergencies, or business travel.
Likewise, there are soccer reasons, usually a rescheduled game in which the referee is a player, which will conflict. These will be accepted as a valid reason for a turn back so long as the referee notifies the assignor within 1-2 days after the game has been rescheduled. This means the referee has to check their schedule online on one of the league websites immediately following their own canceled game and cannot simply claim on Friday night that the "coach just informed me."
Within 48 hours of an assignment, e.g., Thursday for a Saturday assignment, a referee who needs to turn back an assignment MUST make personal contact with the assignor Sending an email or leaving a voice message does not constitute notification to the assignor. You must call and talk.
An email on short notice (less than 48 hours) may mean the match will not be covered, the referee may be fined for being a no-show, and the referee will not receive future offers. Bottom line: Less than 48 hours you must call and talk with the assignor. Leaving a voice mail is the same as leaving an email -- it does not guarantee the message has been received.
If you email the assignor with more than 48 hour notice the subject line must include the words "Turn Back" and the body must include the date, times, and game numbers for the assignments. If you are not unassigned you should contact the assignor again within 24 hours. If the game is on your schedule you are expected to honor the assignment.
Of course, you are always welcome to find your own replacement and we can make the change after the fact.