How to Examine Assumptions in an Opposing Expert's Loss of Earnings Calculation

In a personal injury or clinical negligence claim, an opposing expert’s loss of earnings calculation may rely on assumptions about past earnings, future employment, career progression, retirement, pension benefits and other financial factors.

Reviewing those assumptions can help clarify how a calculation has been prepared and identify areas where further evidence or explanation might be relevant.

The purpose of reviewing an opposing calculation is not necessarily to reach a different figure. Instead, the review may consider whether the assumptions are clearly explained, supported by the available evidence and applied consistently within the calculation.

What Is an Assumption in a Loss of Earnings Calculation?

An assumption is a proposition used when preparing a financial calculation where the eventual outcome cannot be established with certainty.

For example, assessing potential future loss of earnings may require consideration of what the claimant’s earnings and employment position might have been if the injury had not occurred. This can involve historical earnings, employment records, career development and other relevant evidence.

Some assumptions may have a relatively limited effect on the calculation, while others may have a more significant influence on the figures. The relevance of each assumption will depend on the circumstances and evidence available in the individual claim.

Key Assumptions to Examine

Pre-Injury Earnings

The starting point for a future loss calculation may depend partly on the claimant’s earnings before the injury.

Relevant questions may include:

• Which periods of earnings have been considered?
• Are the figures supported by payroll or other financial records?
• Have overtime, bonuses or commission been considered where relevant?
• Have periods of unusually high or low earnings been identified?
• Is the treatment of variable income explained?

Historical earnings may provide useful evidence when considering potential future earnings, but they do not necessarily establish what the claimant would have earned in the future.

Career Progression

An opposing expert’s calculation may include assumptions about how the claimant’s career might have developed without the injury.

This may be relevant where the claimant had a history of promotions, professional qualifications, increasing responsibilities or other evidence of career development.

A review may consider:

• Whether previous promotions are documented
• Whether qualifications or training provide relevant evidence
• Whether employment history supports the assumed career progression
• Whether evidence concerning comparable employment has been considered where appropriate
• Whether alternative career scenarios may need consideration

The available evidence may support different interpretations of future career progression. Any particular scenario should therefore be identifiable as an assumption rather than presented as a certain future outcome.

Retirement and Working Life

Future loss calculations may also depend on assumptions about how long the claimant might have remained in employment.

A review may consider whether the assumed retirement age or working period is clearly identified and whether the available evidence has been taken into account.

Different types of income and employment benefits may also have different assumed durations. The treatment of these periods should be clear within the calculation.

Variable Earnings and Employment Benefits

An opposing calculation may include income or benefits that are not fixed.

Bonuses and Commission

Where bonuses or commission formed part of the claimant’s remuneration, the calculation may need to consider whether and how these amounts are relevant to the assessment of financial loss.

Potentially relevant evidence may include:

• Historical payslips
• Employer payroll records
• Bonus statements
• Employment contracts
• Commission arrangements
• Correspondence concerning remuneration

The review may consider how variable remuneration has been treated and whether the approach is explained by reference to the available evidence.

Benefits in Kind

Employment may provide benefits in addition to basic salary.

Depending on the circumstances, these could include a company car, private medical insurance or other employment-related benefits.

The relevant issue may be whether a benefit has been considered within the financial analysis and, where applicable, how its potential loss has been treated. The appropriate approach will depend on the circumstances of the individual claim.

Evidence Supporting the Assumptions

A review of an opposing expert’s loss of earnings calculation may involve identifying the evidence underlying its principal assumptions.

Depending on the circumstances, relevant material may include:

• Employment contracts
• Payslips and payroll records
• P60s and other tax records
• Pension information
• Employer correspondence
• Promotion records
• Performance information
• Historical bonus or commission records
• Business accounts for self-employed claimants or company directors
• Evidence concerning qualifications and career development

The absence of a particular document does not by itself establish that an assumption is incorrect. It may, however, be relevant when considering what evidence is available to support the assumption.

Checking Consistency Within the Calculation

Individual assumptions can also be considered alongside the wider calculation.

For example, an assessment may include an assumption about increasing earnings while using a different approach when considering associated pension benefits. Similarly, an assumption about the length of a working life may need to be considered alongside assumptions concerning pension accrual or other employment benefits.

A structured review may therefore consider whether:

1. The principal assumptions are clearly identified.
2. The evidence supporting those assumptions can be identified.
3. Related assumptions are applied consistently.
4. The methodology is consistent with the assumptions described.
5. The resulting figures follow from the stated inputs.

This can help distinguish differences arising from assumptions from differences arising from the underlying calculation methodology.

Considering Alternative Scenarios

There may be circumstances in which more than one future outcome could reasonably be considered.

For example, the available evidence may provide different possible indications concerning future promotion, employment progression or retirement.

Rather than treating one outcome as established, the financial analysis may explain the basis for the scenario adopted and, where appropriate, consider whether an alternative scenario is relevant.

The need for alternative scenarios will depend on the evidence and circumstances of the particular claim.

Questions to Consider When Reviewing an Opposing Calculation

A structured review may help identify areas where clarification or further evidence could be relevant.

Earnings

• What earnings figure has been used as the starting point?
• What evidence supports that figure?
• How have bonuses, commission or other variable remuneration been treated?
• Are unusual earnings periods explained?

Career Progression

• What evidence supports the assumed career path?
• Are previous promotions or qualifications relevant?
• Is there evidence concerning potential progression?
• Are alternative scenarios relevant to the evidence?

Working Life

• What assumption has been made about the claimant’s future working period?
• Is the retirement assumption clearly explained?
• Are employment benefits treated consistently with the assumed working period?

Methodology

• Are the principal calculation inputs clearly identified?
• Can the source of significant figures be traced?
• Are the assumptions applied consistently?
• Does the calculation reflect the methodology described in the report?

Reviewing an Opposing Expert Report

A review of an opposing expert report may involve more than comparing the final loss of earnings figure.

The underlying assumptions, source material, calculation inputs and methodology may each need to be considered. This can help establish whether a difference between two calculations arises from a different factual assumption, a different interpretation of evidence or a different calculation approach.

Where the issues are complex, the scope of any financial review will depend on the instructions provided, the available evidence and the issues arising in the individual claim.

For more information about the financial issues that may arise in personal injury claims, see the loss of earnings service and the resources section.

The Role of a Forensic Accountant

A forensic accountant may be instructed in a personal injury or clinical negligence claim to examine financial evidence and undertake analysis relating to alleged financial loss.

Where an opposing expert report has already been prepared, the scope of the work may include examining the assumptions, source material and calculations contained within that report.

The precise role will depend on the instructions, evidence and issues involved in the particular matter. An expert’s analysis should remain within the scope of their expertise and the evidence available to them.

Conclusion

An opposing expert’s loss of earnings calculation may contain assumptions concerning earnings, career progression, retirement, employment benefits and future working patterns.

Examining those assumptions involves more than comparing the final figures. It may involve tracing important assumptions back to the available evidence, considering whether related assumptions are consistent and understanding how they affect the wider calculation.

For legal teams dealing with personal injury or clinical negligence claims, a structured examination of an opposing calculation may help identify financial issues that require clarification, further evidence or expert consideration.

Disclaimer: This article provides general information about financial analysis in personal injury claims. It is not legal or financial advice, and the appropriate approach will depend on the evidence and circumstances of each individual case. Last Reviewed: September 2026