When costs budgeting was first introduced there was a fair amount of uncertainty as to when the budgets should be filed and exchanged (a problem caused by the apparent conflict in wording between the rules and the contents of the directions questionnaire).
The latest version of the rules (coming into force on 6 April 2016 and applying to cases where proceedings are issued after 6 April 2016) provides:
Unless the court otherwise orders, all parties except litigants in person must file and exchange budgets—
(a) where the stated value of the claim on the claim form is less than £50,000, with their directions questionnaires; or
(b) in any other case, not later than 21 days before the first case management conference.”
It is difficult to see the logic behind the different dates for when the budgets should be filed and exchanged. To do so with the directions questionnaire, for lower value claims, is inevitably a costs front-loading step. It is likely to be a more disproportionate additional cost for these lower value claims than it would be for higher value ones. It is also more likely to be an additional wasted cost as lower value claims are, on average, more likely to settle at an early stage in proceedings and often well before a CMC (when a costs management order might actually be made).
The latter problem is compounded by the fact that the courts continue to struggle to list matters for CMCs at an early stage. The consequence of this is that by the time the matter does reach a CMC the earlier costs budgets will often be out-of-date and largely redundant (with the work therefore either being wasted or having to be repeated with up-to-date budgets).
It is unfortunate that the rules have been drafted in such a way as to generate a largely unnecessary and unhelpful front-loading of costs. Unless you are a costs lawyer or law costs draftsman I suppose.