Harris v Moat Housing Group South Ltd – all costs must be claimed in single bill  EWHC 3092 (QB)
Where a party has instructed more than one solicitor on a matter, the costs of both must be included in the bill of costs at detailed assessment. If the costs judge completes his assessment and proceeds to a final certificate without taking the costs of a solicitor into account, there can be no further assessment of the additional costs. CPR 47.6 provides that detailed assessment proceedings are commenced by the receiving party serving both a notice of commencement and a copy of "the" (not "a") bill of costs pursuant to an order entitling him to costs. Para 4.22 of the practice direction states that if different solicitors have represented the receiving party, their respective costs should be set out separately in the bill.
Comment: the problem in this case arose because the receiving party’s solicitors settled the costs claim without reference to the previous firm’s costs. The judge held that the unclaimed costs could not be claimed from the paying party, even though their solicitors had known that the previous firm had done work on the case. This is a highly unusual set of facts but it does illustrate the importance of including all costs in the bill prepared for detailed assessment.
As a postscript on detailed assessment, Master Campbell has held that there is no power available to the court in detailed assessment proceedings under which a paying party can be compelled to produce invoices or accounts in relation to professional services they have used during the course of litigation -Ruttle Plant Hire Ltd v Secretary of State for the Environment  EWHC 90091 (Costs). The receiving party, Ruttle, was thwarted in its attempt to plug holes in its inadequate internal records by reference to the work which DEFRA had undertaken during the litigation.