Defective but not fatal

The Court of Appeal has recently handed down judgment in Duffy v Birmingham City Council [2026] EWCA Civ 146, a case arising from a housing disrepair claim but which ultimately turned on a procedural issue in detailed assessment proceedings.

While the underlying claim concerned housing conditions, the appeal itself addressed a question that will be familiar to practitioners involved in costs disputes: can a defect in the certificate contained within a bill of costs invalidate the commencement of detailed assessment proceedings?

The Court of Appeal’s answer was clear: no. A failure to include express certification of compliance with the indemnity principle may amount to a defect, but it does not render the bill of costs a nullity.

For practitioners involved in housing disrepair and wider civil litigation, the decision provides useful guidance on both the operation of CPR Part 47 and the courts’ increasing reluctance to allow procedural technicalities to derail costs proceedings.

Background: a housing disrepair settlement

The case arose from proceedings brought by the claimant tenant against Birmingham City Council in respect of alleged disrepair.

The claim concluded in October 2022 with a consent order providing that the Council would pay the claimant’s costs, to be assessed if not agreed.

As is standard practice, the claimant subsequently served:

• a Notice of Commencement, and
• a Bill of Costs totalling £26,809.60.

Under CPR 47.9, the paying party then has 21 days to serve Points of Dispute. If they fail to do so, the receiving party may seek a Default Costs Certificate.

That is precisely what occurred. The Council did not serve Points of Dispute within the prescribed period and the claimant obtained a Default Costs Certificate in January 2023.

The Council then sought to set that certificate aside.

The technical challenge

The Council’s challenge evolved during the litigation but ultimately focused on a technical point concerning the form of the certificate contained within the bill of costs.

Although the bill had been signed by the solicitor, one of the certification boxes required by Practice Direction 47 Precedent F had not been ticked. Specifically, the bill did not contain express certification that the costs claimed did not exceed the costs which the receiving party was liable to pay their solicitor – a reflection of the indemnity principle.

The Council argued that this omission rendered the bill invalid, meaning:

• detailed assessment proceedings had never properly commenced; and
• the Default Costs Certificate should therefore be set aside as of right.

The Court of Appeal’s decision

The Court of Appeal rejected that argument.

Giving the leading judgment, Phillips LJ held that although Practice Direction 47 contains mandatory requirements concerning the contents of a bill of costs, not every breach renders the bill invalid.

Instead, the omission created a defective bill, not a nullity.

Importantly, the Court emphasised that a solicitor’s signature on a bill of costs carries significant weight. As officers of the court, solicitors signing a bill implicitly certify that the contents of the bill – including the hourly rates claimed – comply with the indemnity principle. This conclusion is consistent with previous decisions of the Court of Appeal in Bailey v IBC Vehicles Ltd [1998] 2 Costs LR 46 and Gempride Ltd v Bamrah [2018] EWCA Civ 1367.

The absence of a separate tick-box certification did not therefore undermine the validity of the bill.

CPR 3.10 and Procedural Flexibility

Another important feature of the judgment is the Court’s reliance on CPR 3.10, which provides that procedural errors do not automatically invalidate steps taken in litigation unless the court orders otherwise, and that the court may make an order to remedy the error.

The Court endorsed earlier reasoning that treating minor defects as fatal could create disproportionate consequences, potentially encouraging parties to ignore procedural obligations and later rely on technical arguments to derail proceedings.

The correct approach is that alleged defects should ordinarily be addressed through the Points of Dispute process, rather than by treating the bill as void from the outset.

Consequences for the parties

Because the bill of costs was valid, the claimant had been entitled to obtain a Default Costs Certificate when the Council failed to serve Points of Dispute.

The Council therefore failed in its appeal.

However, the Court noted that the Council still retained the possibility of applying to set aside the Default Costs Certificate on discretionary grounds under CPR 47.12(2).

In a pointed observation, the Court also noted that the Council had already incurred over £45,000 in costs pursuing the appeal concerning a bill of approximately £26,000 – raising legitimate questions about proportionality and the use of public funds.

Practical lessons for Costs Practitioners

Although the decision arose from housing disrepair litigation, its implications extend across all civil practice areas where detailed assessment arises.

Three key points emerge:

1. Defects in bills of costs are not automatically fatal: Even where Practice Direction 47 uses mandatory language, breaches will generally render a bill defective rather than invalid.
2. Paying parties must still serve Points of Dispute: If a bill appears defective, the correct course is usually to raise the issue within Points of Dispute.
3. Technical arguments will rarely defeat valid costs proceedings: The courts continue to emphasise substance over procedural technicalities.

Conclusion

Duffy v Birmingham City Council provides useful clarification that technical defects in a bill of costs – including the absence of explicit certification relating to the indemnity principle – will not normally invalidate detailed assessment proceedings.

Instead, such issues should be addressed through the procedural framework established by CPR Part 47, ensuring that disputes over costs are resolved proportionately and efficiently.

Craig Leigh is Founder & Managing Director of 8PP.  If you are dealing with costs issues arising from housing conditions litigation or other civil claims, the team at 8PP Barristers & Associates can help. We regularly assist instructing solicitors with detailed assessment proceedings, costs disputes and strategic litigation advice across a wide range of practice areas. Contact the 8PP team via This email address is being protected from spambots. You need JavaScript enabled to view it. or 0151 245 9292.