Burden of proof is on the employer to establish a failure to mitigate

By Irfana Abbasi, Principal Lawyer

Background

Patricia Kirkland worked for Hawthorn Education Services as an Administration Manager from February 2019 until her summary dismissal on 24 August 2022. The education provider delivers specialist one-to-one support for children outside mainstream education. Ms Kirkland worked part-time, averaging 13.75 hours per week. The employer dismissed her for alleged misconduct but carried out no investigation, followed no disciplinary procedure, failed to provide a written dismissal decision and offered no right of appeal. An Employment Tribunal subsequently found the dismissal unfair and rejected the employer's argument that Ms Kirkland was self-employed.

At a later remedies hearing, Ms Kirkland sought compensation for lost earnings covering a 19-month period following her dismissal. She argued that factors including her age, health issues, lack of a reference and efforts to secure alternative work had affected her ability to obtain new employment. The employer contended that she had failed to mitigate her losses, pointing to the limited number of job applications she had made and her decision to prioritise the development of a short-term property rental business. The Tribunal agreed that she had not adequately mitigated her losses and limited her compensation to six months' earnings.

Ms Kirkland also obtained a preparation time costs order after the Tribunal found that the employer had acted unreasonably during the litigation. Although she claimed 155 hours of additional preparation time, the Tribunal made a broad-brush award of £1,000 without identifying the number of hours it considered recoverable. Ms Kirkland appealed both the reduction in her compensation and the level of the preparation time award.

Outcome

The Employment Appeal Tribunal (EAT) upheld Ms Kirkland's appeal on both grounds. It found that the Tribunal had applied the wrong legal approach when assessing whether she had mitigated her losses. The established legal position is that the burden rests on the employer, as the wrongdoer, to prove that a claimant acted unreasonably in failing to mitigate their loss. The Tribunal instead appeared to place the burden on Ms Kirkland to demonstrate that she had mitigated her losses and failed to make any clear finding that her conduct had been unreasonable. The EAT held that this was an error of law.

The EAT also found that the preparation time award was legally flawed. Employment Tribunal rules require Judges to identify a specific number of hours reasonably spent on preparation and then calculate the award using the statutory hourly rate. The Tribunal had simply awarded a lump sum of £1,000 without carrying out the required calculation or explaining how the figure had been reached. This too amounted to an error of law.

As a result, the EAT set aside both the compensatory award for unfair dismissal and the amount of the preparation time order. The case was remitted to a differently constituted Employment Tribunal to reconsider the questions of mitigation of loss and the value of the preparation time order. Any recalculation of compensation will also require a corresponding review of the 25% ACAS Code uplift previously awarded.

Comments / Key takeaways

This decision serves as an important reminder that employers bear the burden of proving a claimant has failed to mitigate their losses following an unfair dismissal. Tribunals must focus on whether the employee acted unreasonably, not whether they can positively demonstrate that every step taken was reasonable. The EAT reiterated that Employment Tribunals should not apply an unduly demanding standard to claimants who have already suffered a legal wrong.

The Judgment also provides useful guidance on preparation time orders. While Tribunals may adopt a practical approach when assessing time spent by litigants in person, they must still comply with the rules by identifying the hours awarded and applying the statutory hourly rate. Broad-brush figures unsupported by a clear calculation are unlikely to withstand appeal.

For Trade Unions and worker representatives, the case is a reminder to challenge attempts by employers to shift the burden of proof onto dismissed workers when arguing mitigation. It also underlines the value of maintaining detailed records of time spent dealing with litigation, particularly where an employer's unreasonable conduct has increased the work required of a claimant pursuing justice.

Patricia Kirkland v Caroline Mason t/a Hawthorn Education Services [2026] EAT 108.