Rationale for each instance of non-abatement should be fully documented to protect against departmental / external agency criticism. Although the concession deed is the reference point and is considered as the "line in the sand" that parties come back to when agreement cannot be reached, PT10 states that it should be routine to document decisions that vary the administration or implementation of the contract. This can be important, for example, during transition (i.e. from commissioning to operations) where adjustments to business processes may need to be made for practical reasons (RK05). Documenting this type of information can provide a justification for change and leave an audit trail, and thus may protect decision-makers from potential criticism (also see 'Document agreed project decisions for future reference' (treatment for 'Clear and open communication: Shared understanding / trust building')).