There are 125 rule changes coming in 2021. Many of them are just wording changes to increase clarity. Some key changes to note:
1. No more lets. A serve that hits the tape and lands in the correct service box is now live and must be played.
2. Drop serves allowed. Serves may be hit after the ball bounces and with no restrictions on the nature of the swing.
To see the whole document and changes for 2021, please go to: https://usapickleball.org/wp-content/uploads/2019/12/Updated-2021-Change-Document-FINAL.pdf

New in 2021 is the Alternate Rulebook,  an attempt to simplify how the rules are presented.  The Alternate Rulebook can be used in any venue other than tournaments, without restriction. The Alternate Rulebook will enjoy the benefit of a one-year public comment period. Please use the site below:
https://usapickleball.org/wp-content/uploads/2020/12/2021-Alternate-Rulebook-12-16-20-FINAL.pdf