SIGNIFICANT RULE CHANGES FOR 2023 

Apparel (2.G.1/2.G.4) Inappropriate apparel may now include apparel that approximates the color of the tournament ball. Section 1 encourages players to avoid wearing apparel that approximates the color of the ball. The Tournament Director retains the right to require an apparel change during a non-chargeable time-out.
Spin Serve (4.A.5) Manipulating the ball to add spin during the release of the ball is not allowed. Some natural rotation of the ball when it is released is allowable but the server must not impart manipulation or spin prior to striking the ball to serve. This applies to the volley serve and the drop serve.
Replay or Fault on the Serve (4.A.6/4.A.9) The referee has the authority to immediately stop play and order a replay if the referee is not certain that one more required elements of a serve have been met. The referee will call an immediate fault if a serve clearly violates one or more of the requirements. The intent is to induce players to adjust their serve so that it clearly and obviously meets all requirements.
Player Questions about Correct Server, Receiver or Position (4.B.8) Player questions about correct server, receiver or position remain allowed before the serve is hit. A generic question by the server such as “Am I good?” is considered to encapsulate both the correct server question and the correct position question, and the referee will answer both questions. In non-officiated play, a player may ask the opponent the same questions and the opponent must respond with the appropriate information.  
Wrong Score Called (4.K) If the wrong score is called, the referee or any player may stop play before the return of serve to correct the score. It is a fault to stop play after the return of serve to identify or ask for a score correction. It is a fault to stop play to identify or ask for a score correction when the score was correctly called.
Equipment Time-Out (10.D) Players are not required to use a regular time-out for equipment adjustments or changes necessary for fair and safe continuation of the match. The referee will call an equipment time-out of a reasonable duration.

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All rule changes can be found http://www.usapa.org/rulebook