Under CPR 47.50(10), a party who requests an oral hearing following a provisional assessment must achieve an adjustment of at least 20% in its own favour on the sum provisionally assessed, or it will be ordered to pay the costs of an incidental hearing. Falling short of that threshold, even by a small margin, means paying for a hearing that produced little or no benefit.

This 20% rule is one of the sharpest tactical decision points in provisional assessment, and it’s worth understanding properly before deciding whether to challenge an outcome you’re unhappy with.

Provisional Assessment and the 20% Threshold

CPR 47.15 governs provisional assessment, the paper-based procedure used for bills of costs valued at £75,000 or less, introduced as part of the Jackson Reforms in April 2013. Once a bill has been assessed on the papers, the court sends the annotated bill to each party. Either party that is dissatisfied with the outcome may request an oral hearing, but must do so within 21 days of receiving the notice, under CPR 47.15(7) and (8).

The catch is CPR 47.15(10). Requesting an oral hearing removes the £1,500 costs cap that applies to provisional assessment, meaning a significantly higher amount of costs can be incurred at the hearing itself. If the party requesting the hearing fails to improve its position by 20% or more of the sum provisionally assessed, it will ordinarily be ordered to pay the costs of an incidental to that hearing, even if it achieves some improvement below that threshold.

This is a deliberately high bar. It reflects the court’s reluctance to let parties re-litigate a provisional assessment without a genuinely compelling case for doing so.

Working Out Whether It’s Worth Challenging

Before requesting an oral hearing, it’s worth calculating realistically what a 20% swing would actually mean in cash terms, and weighing that against the now-uncapped costs of the hearing itself. A bill provisionally assessed at £30,000 needs to move by £6,000 or more in the challenging party’s favour to avoid the adverse costs consequence and the costs of arguing for that movement at an oral hearing can easily exceed the sum in dispute.

This is why the 20% threshold functions as a genuine filter. It’s designed to discourage marginal challenges and reserve oral hearings for cases where the provisional assessment has gone meaningfully wrong, not simply produced a result one party would have preferred to avoid.

The Wider Provisional Assessment Process

The 20% rule sits within a broader procedure. Before an application for provisional assessment can be made, the receiving party must have served a compliant bill of costs together with the notice of commencement, after which the paying party has 21 days to serve Points of Dispute. Once negotiations have been exhausted, an application is made on Form N258, ticking the box for provisional assessment, along with the bill, proof of entitlement to costs, Points of Dispute, and any Replies, and any Part 36 offers submitted separately as confidential.

Applications must generally be made within three months of the deadline set out in CPR 47.14, missing which the paying party may seek an unless order, or the court may disallow interest for the period of delay under CPR 47.14(4).

Part 36 and the 20% Rule Are Separate Mechanisms

Its worth keeping the 20% threshold distinct from the consequences of beating a Part 36 offer. Where a receiving party has made a valid Part 36 offer and beats it at final assessment, CPR 36.17 provides for a 10% uplift on the assessed costs, enhanced interest, and indemnity basis costs, a different mechanism entirely from the 20% oral hearing threshold under CPR 47.50(10), and the two shouldn’t be confused when weighing up whether to challenge a provisional outcome.

Frequently Asked Questions

What happens if a bill is reduced by more than 20% on assessment? If a party requests an oral hearing following provisional assessment and achieves an adjustment of 20% or more in its favour, it will not be ordered to pay the costs of that hearing. Falling short of 20% means paying those costs, even if some improvement was achieved.

Does the 20% threshold apply to all detailed assessments? No. It applies specifically to oral hearings requested following a provisional assessment under CPR 47.15, which is used for bills of £75,000 or less. It doesn’t apply to bills proceeding directly to a full detailed assessment hearing.

Is there a cost cap on provisional assessment? Yes. Recoverable costs of a provisional assessment are capped at £1,500 plus VAT and court fees. That cap no longer applies once an oral hearing is requested.

How long do I have to request an oral hearing? 21days from receipt of the notice of the provisional assessment outcome, under CPR 47.15(7).

How Greener Costs Can Help

Our team of costs lawyers and costs drafters advises on whether challenging a provisional assessment outcome is worth pursuing, prepares requests for oral hearings, and represents both receiving and paying parties through the provisional assessment process.

If you’re weighing up whether to challenge a provisional assessment outcome, contact Greener Costs today. Call us on 01204263047 or email info@greenercosts.co.uk.