Agent's are advised when making a bid to sell a property that they cannot change between fixed and percentage commission structures once they have made a decision as to which type they are offering. This keeps it simple to track how an agent's bid is compared to others.
If a seller has a preference for the type of commission they wish agents to offer this should be addressed in the Sale brief published with the opportunity.
Agents who need to change between fixed and percentage commission because of a seller request should contact support.