Solicitors Act Assessment and the One-Fifth Rule Explained

Updated 11 March 2026

A Solicitors Act assessment allows a client to challenge the amount of a solicitor’s bill by asking the court to review the charges. The procedure arises under section 70 of the Solicitors Act 1974 and is commonly used where a client disputes whether the fees charged are reasonable

One of the key rules governing these assessments is the “one-fifth rule”, which determines who pays the costs of the assessment. Broadly speaking, if the client succeeds in reducing the solicitor’s bill by 20% or more, the solicitor may be required to pay the costs of the assessment. If the reduction is less than 20%, the client will usually have to pay those costs.

Understanding how this rule operates is important for both solicitors and clients considering a Solicitors Act challenge.

What Is a Solicitors Act Assessment?

A Solicitors Act assessment is a court process used to review the amount payable under a solicitor’s bill of costs. It is separate from the detailed assessment process under CPR Part 47, which normally concerns costs between litigating parties rather than disputes between a solicitor and their own client.

Where a client disputes a solicitor’s bill, the court may examine whether the charges were properly incurred and whether the amount claimed is reasonable.

The process therefore provides a mechanism for resolving disputes about professional fees and ensuring that the costs charged are justified.

The One-Fifth Rule Under the Solicitors Act

Section 70(9) of the Solicitors Act contains the rule commonly referred to as the “one-fifth rule”.

In simple terms:

• If the bill is reduced by 20% or more, the solicitor will normally pay the costs of the assessment.

• If the reduction is less than 20%, the client will usually have to pay the costs of the assessment.

  
  

This rule creates an important tactical consideration for clients considering whether to challenge a solicitor’s bill. If the reduction achieved is relatively modest, the client may ultimately be responsible for the costs of the assessment proceedings themselves.

However, the rule is not absolute. Courts retain discretion to depart from it where special circumstances exist.

Special Circumstances and the Court’s Discretion

Section 70(10) of the Solicitors Act allows the court to depart from the one-fifth rule where there are special circumstances relating to the bill or the conduct of the assessment.

These circumstances may include factors such as:

• the way in which the assessment was conducted

• whether unnecessary issues were raised

• whether the dispute significantly increased the costs of the hearing

• the overall conduct of the parties

  
  

Where such factors arise, the court may adjust the normal costs consequences of the assessment.

The Court of Appeal Decision in Wilsons v Bentine

The application of the one-fifth rule was considered in detail by the Court of Appeal in Wilsons Solicitors LLP v Bentine and Stone Rowe Brewer v Just Costs Ltd [2015] EWCA Civ 1168.

In the Bentine case, solicitors had delivered a bill of approximately £145,000. Following assessment, the court allowed about £95,000, representing a reduction of more than 20%.

Ordinarily this would mean the solicitor should pay the costs of the assessment under the one-fifth rule. However, the costs judge found that special circumstances existed due to the way the client had conducted the proceedings, which had significantly increased the costs of the assessment.

As a result, the solicitor was ordered to pay 60% of the client’s costs, demonstrating how the court’s discretion can alter the normal outcome.

The Court of Appeal ultimately confirmed that the Solicitors Act operates as a self-contained statutory scheme, and that the natural meaning of the statute should be applied when determining the operation of the one-fifth rule.

The Stone Rowe Brewer Case

The related case of Stone Rowe Brewer v Just Costs Ltd involved bills totalling approximately £33,000, of which about £20,000 was disputed. The parties eventually settled the dispute for £23,700, representing a reduction of roughly 30%. Despite the reduction exceeding the one-fifth threshold, the costs judge considered that the solicitors had succeeded on the principal issue raised in the dispute and ordered the client to pay 70% of the solicitors’ costs of the assessment.

On appeal, the High Court concluded that insufficient weight had been given to the reduction achieved and overturned that decision.

The case demonstrates that the court will examine the overall circumstances of the dispute, rather than applying the one-fifth rule mechanically.

Practical Implications of the One-Fifth Rule

The key lesson from these decisions is that the 20% threshold is not the only factor determining the costs consequences of a Solicitors Act assessment.

Courts will also consider:

• the issues raised in the assessment

• the conduct of the parties

• whether the dispute unnecessarily increased the length or complexity of the hearing

  
  

Where complex or unusual issues are raised, the court may depart from the normal rule and adjust the costs order accordingly.

Managing Costs Disputes Effectively

Solicitors Act assessments remain relatively uncommon, but when they do arise they can be procedurally complex and expensive.

Clear communication with clients about fees and regular updates regarding costs can significantly reduce the risk of disputes escalating to this stage.

Where costs disputes do arise, specialist advice can help parties understand the potential consequences of the one-fifth rule and the court’s discretion regarding costs.

For a broader explanation of how courts assess legal costs generally, see our Detailed Assessment of Costs Guide.