Changing a confirmed split requires all parties to re-confirm — it can't be edited unilaterally.
5.10.1 Editing a live split
Propose the new percentages from the track's Royalty Splits page. The edit is sent to every party on the existing split for re-confirmation — the change does not take effect until all parties accept the new terms.
5.10.2 Removing a collaborator
Removing a party from a split also requires that party's confirmation, since it changes their royalty entitlement going forward. An exception exists for splits where a collaborator's account has been inactive for an extended period — contact support for this specific scenario.
5.10.3 What happens to pending payouts during an edit
Royalties already calculated under the prior split terms, but not yet paid out, are settled under the terms that were active at the time they were earned — an in-progress edit does not retroactively change them.
Source: MadDesk article 5.10 (5-10)