A new revision (24) of Contest Rules has just been posted as Standing Order 6.
Amongst the rule changes are:

Rule 1.14 - Removal of the 75/25 ratio for mixed choruses – now just requires two different gender identities without any minimum ratio

Rule 1.17 – clarification that an Invitational quartet or chorus cannot compete, just perform for evaluation, and that scores won’t be published for them

Rules 3.2.5 and 3.3.5 – reinstatement of the one year stand down rule for Open Quartet and Chorus Champions – this previously applied until 2020 (removed during COVID period) - will re-apply from 2024 on (not retrospective to 2023)

Rule 3.2.6 – clarification that a previous Open Champion quartet can compete with more than two members, just not in their stand down year

Rule 3.3.3 – clarification that choruses with common members must satisfy the 75/25 rule as if in Open competition
 

Rule 4.2 – change to entry closure for National contest to 28 days before contest

Rules 7.1.13, 7.1.15, 7.1.20 – removal of gender divisions for youth quartets, and most improved divisions for quartet and chorus