A few links to help you through the latest REF guidance:
Including: Some clarification on staff who have significant responsibility for research, portability of outputs, some variation in the rules for co-authored output and clarification that there are no advantages or disadvantages in flagging a work as interdisciplinary.
Blog post from Catriona Firth of Research England “The REF guidance isn’t trying to catch you out”
Blog post from Stephen Hill of Research England “Reflecting on the guiding principles for REF2021”
Six important things you need to know about impact from the REF2021 guidance by Mark Reed on the LSE Impact blog