Red Tractor have put together a guidance document which covers frequently asked questions and provides examples of how standard OT.a can be met.
Access the guidance here
Along with trailer identification number, a Red Tractor membership number is required to be displayed on trailers used for off-farm transport to ensure traceability throughout the supply chain. Displaying membership and trailer numbers allows members to use their own trailers to deliver grain off-farm without being a member (and paying membership fees) of another assurance scheme.