Is the One-Fifth Rule King in Solicitors Act Assessments?

The decision in Clare Griffin v Kleyman & Co Solicitors Ltd [2026] EWHC 257 (SCCO) is a timely reminder of the continued force of the one-fifth rule in Solicitors Act assessments. Even where a client secures a significant reduction in their solicitor’s bills, that does not necessarily mean they will avoid liability for the costs of assessment. The case also provides further guidance on when “special circumstances” under s.70(10) of the Solicitors Act 1974 may displace the statutory presumption under s.70(9).

Introduction: The One-Fifth Rule in Solicitors Act Assessments

Solicitor-own client disputes are notoriously difficult matters. They are usually brought by clients who are unhappy with the costs invoiced by their instructed solicitor and are seeking to reduce the amount they have to pay. The right for a client to challenge the costs of their solicitor has been enshrined in legislation dating back centuries. Its current legislative form is now over half a century old and can be found in the Solicitors Act 1974.

However, despite that right existing in favour of clients, there are provisions within the Solicitors Act 1974 which arguably favour solicitors in such assessments. One of the clearest examples is contained within s.70(9) of the Solicitors Act 1974, which sets out the one-fifth rule.

The one-fifth rule provides that unless the client is able to reduce a solicitor’s bill by 20% or more, the client will be liable to pay the solicitor’s costs of the assessment.

This is a particularly high bar to reach. Solicitors Act assessments are carried out on the indemnity basis, meaning the burden of proof lies on the client to show that costs were unreasonably incurred or unreasonable in amount, with the benefit of any doubt resolved in the solicitor’s favour.

It is therefore essential for any client to undertake a realistic cost-benefit analysis before seeking such an assessment. Any reduction achieved may very easily be wiped out by an order to pay the solicitor’s costs of the assessment, alongside their own costs of the assessment.

Can the Court Depart from the One-Fifth Rule?

Section 70(10) of the Solicitors Act 1974 does provide that the Court may depart from the one-fifth rule in s.70(9) if special circumstances can be established.

In Angel Airlines SA v Dean & Dean [2008] EWHC 1513 (QB), Coulson J set out the position that “a clear without prejudice offer, made in proper time and in proper form” may establish special circumstances for the purposes of s.70(10) and reverse the application of the one-fifth rule.

However, it is also established that Part 36 offers do not apply in Solicitors Act assessments, following the decision of Costs Judge Leonard in Zuhri v Vardags Ltd [2023] EWHC 3050 (SCCO).

Costs Judge Leonard has now provided further clarification on the types of offers which could — and, importantly, could not — reach the threshold of special circumstances under s.70(10) of the Solicitors Act 1974 so as to displace or reverse the one-fifth rule.

The Background to Clare Griffin v Kleyman & Co Solicitors Ltd [2026] EWHC 257 (SCCO)

In this matter, the Claimant sought a Solicitors Act assessment in respect of costs incurred in her divorce proceedings.

The bills raised totalled £181,954.64 (including VAT and disbursements) and were assessed at £154,039.94, a reduction of £27,914.70 (15.34%).

The Claimant had paid £174,309.82 against those bills and was therefore due a refund of £20,269.88.

The key question to be determined by Costs Judge Leonard was: who should be liable for the costs of the assessment?

Costs Judge Leonard heard representations and considered the two key offers made by the parties.

The Claimant’s Offer and the Defendants’ Response

The Claimant’s offer came shortly after the order for costs to be assessed was agreed. It was made in the form of a Part 36 offer on the following terms:

“Our client will accept £28,000.00 in full and final settlement of her Part 8 Claim. This offer includes interest to the date of acceptance or expiry of the period for acceptance of this offer. If this offer is accepted, the payment to our client will be £17,547.18 once the amount you are owed in accordance with your witness evidence is deducted (£10,452.82 was the outstanding sum to be paid by the Claimant)…

If the offer is accepted within 21 days of service of this offer, the defendant will be liable for the claimant's costs in accordance with rule 36.13…

If you choose not to accept this offer, but our client obtains judgment which is at least as advantageous as this offer, our client will rely on the consequences set out under CPR 36.17.”

The Defendants responded by raising concerns that the offer did not amount to more than a 20% reduction to the bills of costs and that, therefore, the Claimant would not be entitled to a costs order in her favour under the one-fifth rule.

The Defendants subsequently made a drop hands offer on the basis that there be no order as to costs and that they would not seek payment of the £10,452.82 which remained outstanding.

They also noted that, at the time, their costs of assessment were in the region of £10,000.

The Costs Decision in Clare Griffin v Kleyman & Co Solicitors Ltd [2026]

Costs Judge Leonard considered the position and accepted the principle that the making of a clear without prejudice offer, made in proper time and proper form, can amount to a special circumstance sufficient to reverse the statutory presumption created by the one-fifth rule.

Furthermore, if such an offer is more advantageous to the offeree than the eventual outcome of the assessment, that would offer strong grounds for the Court to depart from the usual rule.

However, when considering whether an offer is truly more advantageous, Costs Judge Leonard made clear that the billing refund cannot be considered in isolation.

Instead, the Court must take a holistic view of the overall position, including:

• the reduction achieved at assessment
• the operation of the one-fifth rule under s.70(9)
• and the likely costs liability for the assessment itself

Ultimately, Costs Judge Leonard found that the offer made by the Claimant was not sufficient to meet the threshold of special circumstances under s.70(10) so as to displace the application of the one-fifth rule.

This was primarily because the offer included a term requiring the Defendants to concede their right to the costs of the assessment and instead pay the Claimant’s costs of assessment, despite the fact that the Claimant would not have been entitled to such an outcome under the one-fifth rule.

As such, the Defendants were awarded their costs of assessment, to be paid by the Claimant.

A Separate Costs Point: The Defendants’ Costs Were Capped

On a separate point, the Defendants’ costs of assessment were to be capped at 80% of those incurred.

This followed a finding of negligence in the Defendants’ record and account keeping, which resulted in £4,334.10 being included within the bill that the Claimant was never required to pay.

That issue did not alter the application of the one-fifth rule, but it did affect the extent of the Defendants’ recovery of their own costs of assessment.

Why Clare Griffin Matters: The One-Fifth Rule Remains a Major Hurdle

This is a further positive result for solicitors seeking to protect themselves against clients pursuing Solicitors Act assessments.

The decision of Costs Judge Leonard provides protection against opportunistic clients making offers of less than a 20% reduction to the solicitor’s costs and then attempting to recover their own costs of assessment as a result.

On the other hand, it is arguable that this is another decision which may further limit consumer protection where clients seek to challenge their solicitor’s costs.

Either way, the message is clear: the one-fifth rule remains a major hurdle in Solicitors Act assessments.

Key Takeaways for Solicitors Act Assessments

Now more than ever, careful consideration is required when advising clients who are considering a Solicitors Act assessment.

In the vast majority of circumstances, there is a significant burden to overcome, and it is important that regular cost-benefit analysis is undertaken so that the client is fully informed of their potential costs liability if they fail to reduce the bills by 20% or more.

In many cases, the reductions that could be achieved at assessment are likely to fall below the one-fifth threshold. Proper calculations should therefore be provided to clients setting out:

• the likely reductions that could be achieved
• the effect of the one-fifth rule
• and the potential costs of assessment liability they may be required to pay

Additionally, if a client does embark on a Solicitors Act assessment and wishes to make an offer, careful thought should be given to:

• where the offer is pitched
• what terms are included
• and how the offer will be assessed against the likely overall outcome

As illustrated in this case, the inclusion of a single term can inadvertently affect the value of the offer and the threshold which would need to be achieved at assessment in order to beat it.

A Final Thought: Could a Different Offer Have Changed the Outcome?

Finally, it is an interesting thought experiment to consider what may have happened if the Claimant had instead offered a 15% reduction to the costs claimed while agreeing to pay the solicitors’ costs of assessment, and then gone on to achieve a 16–19% reduction at assessment.

Would the Court have found that such an offer was more advantageous to the client overall, and therefore sufficient to amount to special circumstances under s.70(10) so as to reverse the application of s.70(9)?

Based on Costs Judge Leonard’s comments, the answer is possibly — but the Court would still need to take a full view of the offers and the assessment outcome as a whole before reaching that conclusion.

That, in itself, is perhaps the most useful practical takeaway from Clare Griffin v Kleyman & Co Solicitors Ltd [2026] EWHC 257 (SCCO): in Solicitors Act assessments, the question is not simply whether a client “wins” a reduction, but whether the overall commercial outcome is genuinely better.

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