ADRG01600 - The parties in the dispute have ultimate control
It is for the customer and the HMRC officers to reach an agreement that both sides can accept. The role of the mediator is to facilitate that process, not to impose a solution, or make direct suggestions, although the mediator will encourage both sides to think creatively and will help them consider all the possible options for settling the dispute.
Mediators are trained to help people understand the realities of their situation and help steer them towards areas where agreement is possible. Often it comes down to both sides properly identifying the relevant facts and focusing on them, clarifying the technical position together, at which point the way forward often becomes clearer.
At the end of the mediation the customer and the HMRC officers, not the mediator, decide together what can be agreed and what will remain in dispute.