5.6 Service providers will often be party to interface arrangements with other subcontractors on the project. For instance, there may be interface arrangements in place between the construction subcontractor and other service providers, or between soft service providers themselves. The bid and transfer arrangements will need to cover any new contractor's entry into these interface arrangements. Although these interface arrangements are not part of the services actually being tested, they are a necessary part of the process of inserting the new contractor into the project. The Authority should, at the outset of the PFI transaction or tender process, as part of its due diligence, ensure that the relevant interface agreements have Deeds of Accession in a pre-agreed format attached to them, in order to provide a simple mechanism for new or replacement parties to join the contract. Failure to have such mechanisms in place could undermine the market test.