Meta description: The Supreme Court confirmed part-time workers can claim discrimination when their status is an effective cause of less favourable treatment. Expert advice from UK employment solicitors.
The Supreme Court has delivered an important judgment for employers and part-time workers in Augustine v Data Cars Ltd [2026] UKSC 30.
On 12 August 2026, the Court unanimously confirmed that a part-time worker does not need to prove that their part-time status was the sole cause of less favourable treatment. It is enough to show that part-time status was an effective cause : meaning that it significantly influenced or materially contributed to the treatment.
The decision rejects the restrictive approach previously associated with McMenemy v Capita Business Services Ltd and lowers the causation threshold for claims under the Part-time Workers (Prevention of Less Favourable Treatment) Regulations 2000.
For employers, the message is clear: a policy can create legal risk even if it applies in identical terms to full-time and part-time staff. Businesses should review pay structures, deductions, benefits and rostering arrangements now.
What was Augustine v Data Cars about?
Mr Augustine worked as a part-time private hire driver for Data Cars Ltd. Drivers paid a fixed weekly “circuit fee” of £148 for access to the company’s booking and dispatch system.
The same flat fee applied to full-time and part-time drivers. However, because Mr Augustine worked fewer hours, the fee represented a larger proportion of his earnings and reduced his effective hourly rate more significantly than it did for full-time drivers.
Mr Augustine argued that this amounted to less favourable treatment under the 2000 Regulations.
The Employment Tribunal rejected the claim. It considered that the fee had not been imposed solely because Mr Augustine was a part-time worker. The fee was applied uniformly and was also connected to the company’s operating costs.
The case ultimately reached the Supreme Court, which had to decide whether the “sole cause” test was correct.
The Supreme Court’s ruling
The Supreme Court held that regulation 5 of the 2000 Regulations is engaged where part-time status is an effective cause of less favourable treatment.
Part-time status does not have to be:
- The only reason for the treatment;
- The main reason for the treatment; or
- A reason expressly stated in the employer’s policy.
A worker must still establish that they have been treated less favourably than a comparable full-time worker and that their part-time status was an effective cause of that treatment. However, they no longer need to prove that part-time work was the exclusive reason.
The Court disapproved the “sole-ground” approach in McMenemy v Capita Business Services Ltd [2007] IRLR 400. That decision had created a significant barrier for part-time workers because many employment decisions have more than one reason behind them.
The Supreme Court’s judgment is available through the official Supreme Court case page, while the Regulations can be read on legislation.gov.uk.
What does “effective cause” mean?
An “effective cause” test recognises that workplace decisions are rarely based on a single factor.
For example, an employer may introduce a fixed charge because:
- It is administratively simple;
- It helps recover a genuine business cost; and
- It applies to all workers using a particular service.
Those reasons may be genuine. However, if the fixed charge places a disproportionate financial burden on part-time workers because they work fewer hours, part-time status may still be an effective cause of the disadvantage.
The question is not simply whether the employer intended to discriminate. The focus is on the connection between the worker’s part-time status and the less favourable outcome.
Similarly, a rostering policy may apply to everyone but have a particular impact on part-time workers. If part-time status materially contributes to the disadvantage, regulation 5 may apply.
The fact that not every part-time worker suffers the same disadvantage is also not necessarily decisive. A part-time worker who is adversely affected may still bring a claim if their part-time status is an effective cause of the treatment.
The Part-time Workers Regulations 2000
The Regulations give part-time workers the right not to be treated less favourably than comparable full-time workers.
Regulation 5 provides protection where:
- The worker is treated less favourably than a comparable full-time worker;
- The treatment is on the ground that the worker is part-time; and
- The treatment is not objectively justified.
The Regulations also reflect a pro rata principle. This generally means that part-time workers should receive terms and benefits proportionate to those available to comparable full-time workers, unless different treatment can be justified.
Part-time worker protection is separate from claims under the Equality Act 2010. A worker does not need to establish that the treatment was related to sex, race, disability, age or another protected characteristic.
This distinction matters. Part-time status itself is not a protected characteristic under the Equality Act. It is protected under the specific 2000 Regulations.
The claim is also different from an unfair dismissal claim. A dismissal may be unfair for reasons connected with the employee’s part-time status, but the applicable legal tests and time limits are not the same. Anyone considering a dismissal claim should obtain advice promptly from unfair dismissal solicitors in the UK, particularly because employment tribunal limitation periods are short.
Why uniform policies may still create risk
One of the most important aspects of Augustine is that a policy does not have to mention part-time workers to create a potential claim.
A rule that applies equally “on paper” may produce unequal outcomes in practice. Examples may include:
- A flat administration, equipment or membership fee;
- A fixed deduction from salary;
- A bonus requiring a minimum number of hours;
- An allowance that is not calculated pro rata;
- A benefit available only to employees working a particular schedule;
- A bank holiday or leave rule that disadvantages workers who do not work standard Monday-to-Friday hours;
- A requirement to attend mandatory meetings outside a part-time worker’s agreed hours;
- A rostering system that repeatedly allocates undesirable shifts to part-time staff;
- A promotion or training requirement based on availability rather than performance.
The Supreme Court’s reasoning means that employers should look beyond the wording of a policy and consider its actual effect.
A uniform charge may appear neutral, but the economic impact may be substantially greater for a part-time worker. A uniform availability requirement may also disadvantage workers whose contractual hours are limited.
Objective justification is now likely to be the main battleground
The judgment does not mean that every difference affecting a part-time worker is unlawful.
Employers may have a defence where the treatment is objectively justified. In broad terms, this requires the employer to show that the treatment:
- Pursues a legitimate objective; and
- Is a proportionate means of achieving that objective.
A general assertion that “this is how the business operates” is unlikely to be enough. Employers should be able to explain the commercial or operational aim behind the policy and demonstrate why the particular approach is reasonably necessary.
For example, an employer relying on a flat charge may need to consider:
- What cost the charge is intended to recover;
- Whether the cost could be calculated according to usage or hours worked;
- Whether a pro rata alternative would achieve the same objective;
- Whether the policy has been reviewed using reliable workforce data;
- Whether less disadvantageous alternatives were considered.
The existence of other business reasons may be relevant to objective justification and, potentially, compensation. However, those reasons do not automatically defeat liability at the causation stage.
What should HR teams review?
Employers should consider carrying out a targeted audit of their treatment of part-time staff. The review should include:
Pay and deductions
Check whether part-time employees receive pay, allowances, bonuses and commission on a proportionate basis. Review fixed deductions, training charges, parking fees, equipment costs and professional membership fees.
Benefits
Consider whether benefits such as private medical cover, life assurance, company cars, sick pay or other contractual benefits are available fairly. Some benefits may legitimately be provided on a different basis, but the reasoning should be documented.
Holiday and time off
Review holiday calculations, bank holiday arrangements and rules restricting when leave can be taken. Particular care is needed for employees who do not work every day of the week.
Rostering
Examine whether shift allocation systems disadvantage part-time workers or repeatedly place them on less desirable shifts. Employers should also consider whether mandatory meetings, training or events are compatible with contracted working patterns.
Career progression
Check whether promotion, training and overtime opportunities depend on assumptions about full-time availability rather than objective performance or genuine business requirements.
Records and decision-making
Managers should record the reasons for decisions affecting part-time workers. Clear records may assist the employer in demonstrating that a policy pursues a legitimate aim and is proportionate.
What should part-time workers do?
Part-time workers who believe they have been treated less favourably should gather relevant evidence, including:
- Contracts and written policies;
- Payslips and records of deductions;
- Rosters and time records;
- Bonus or commission documents;
- Emails and messages explaining workplace decisions;
- Evidence of how comparable full-time workers were treated.
A worker should usually raise the issue promptly, either informally or through the employer’s grievance process. However, internal discussions do not necessarily stop the employment tribunal time limit running.
Before bringing a tribunal claim, an individual will generally need to notify Acas for early conciliation. Time limits are strict, so early legal advice is important.
What does the decision mean for employers?
Augustine v Data Cars is not a decision limited to private hire businesses. Its reasoning is relevant to employers across sectors, including retail, hospitality, transport, healthcare, professional services and small businesses.
The immediate risk is not that every existing policy is unlawful. The risk is that employers may have relied on the wrong causation test when assessing potential exposure.
A policy that would previously have survived because part-time status was not the sole reason for the treatment may now require a closer examination of its practical impact and objective justification.
Employers should therefore avoid relying solely on statements such as:
- “The rule applies to everyone”;
- “We did not intend to treat part-time workers differently”; or
- “There were other business reasons for the decision.”
Those points may be relevant, but they are not necessarily a complete answer under the effective-cause test.
How Tyndel Solicitors can help
The Supreme Court’s decision creates a timely opportunity for employers to review their contracts, policies and working practices. It also strengthens the position of part-time workers who have experienced disadvantage at work.
Tyndel Solicitors provides practical employment law advice to businesses and individuals across England and Wales. Our employment law solicitors can advise on part-time worker rights, workplace policies, grievances, discrimination risks, settlement discussions and tribunal claims.
If you are an employer reviewing your arrangements, or a worker concerned about less favourable treatment, contact Tyndel Solicitors’ Employment Law team for clear, focused advice.
This article provides general information about Augustine v Data Cars Ltd [2026] UKSC 30 and is not a substitute for advice on the facts of a specific case.
