PD 47 para.13.10 allows a party to vary their bill:
“(1) If a party wishes to vary that party’s bill of costs, points of dispute or a reply, an amended or supplementary document must be filed with the court and copies of it must be served on all other relevant parties.
(2) Permission is not required to vary a bill of costs, points of dispute or a reply but the court may disallow the variation or permit it only upon conditions, including conditions as to the payment of any costs caused or wasted by the variation.”
It is in the court’s discretion as to whether to disallow the variation. For a case proceeding to a detailed assessment hearing this is straightforward enough. The court can rule on this issue, if it is contentious, at the start of the hearing.
But what about a case going to provisional assessment? Does that require an application is advance of the provisional assessment, despite permission not being required to make the variation itself? Will the court even know there has been a variation if only the amended bill is filed with the court?