A part-time employee works three days rather than five. That may change the amount of annual pay or leave they receive, but it does not make every difference lawful. Part-time workers’ rights protect employees and workers from less favourable treatment because they work part time, unless the employer can objectively justify it. The practical task is to identify the right full-time comparator, compare each term properly and distinguish a proportionate calculation from an exclusion.
Start with the treatment being compared
There is no statutory number of weekly hours that automatically makes someone part time. ACAS describes a part-time employee or worker as someone who works fewer hours than a full-time employee or worker in the same organisation. The protection comes from the Part-time Workers (Prevention of Less Favourable Treatment) Regulations 2000.
Identify the particular treatment: hourly pay, bonus, pension access, holiday, sick pay, training, promotion, transfer, career break or redundancy. Then ask whether the person is worse off than an appropriate full-time comparator because they are part time.
A difference caused by job content, grade, skills or location may have nothing to do with part-time status. A rule excluding everyone who works fewer than 30 hours directly raises the question the Regulations are designed to answer.
Choose an actual, legally relevant comparator
The comparator must be a full-time worker employed by the same employer, working under the same type of contract and doing the same or broadly similar work. Qualifications, skills and experience can be relevant. The comparison is normally made within the same establishment; if there is no suitable comparator there, a full-time worker at another establishment may be used.
The Regulations distinguish contract types, including employees, casual workers and apprentices. Do not compare a part-time employee with a self-employed contractor or assume that a similar title is enough. Record the comparator, location, contract type and why the work is the same or broadly similar.
If a small business has no full-time equivalent, that statutory comparison may not be available. The employer should still check contractual consistency, minimum rights and discrimination risks.
Part-time Workers Regulations 2000 ↗ · Related guide: fixed-term contracts →
Use pro rata where it produces proportionate treatment
Pro rata means in proportion to hours worked. If a full-time comparator earns £30,000 for 37.5 hours a week, a colleague doing the same role for 22.5 hours would ordinarily receive £18,000: the same hourly rate, adjusted to 60% of full-time hours. A £1,000 contractual bonus might similarly become £600.
Regular-hours part-time workers remain entitled to 5.6 weeks’ statutory paid holiday. The number of days or hours will be lower where they work fewer days or hours, but the entitlement in weeks remains equivalent. Employers offering more than the statutory minimum should normally apply that enhanced entitlement proportionately too.
Do not use ‘pro rata’ as a catch-all. Training access, promotion opportunities and the hourly pay rate are not benefits that can simply be reduced by the hours fraction. Overtime is a specific exception: ACAS says part-time staff are not entitled by law to an overtime premium until they have worked more than the normal hours of full-time staff, although the contract or policy may provide something better.
GOV.UK: part-time workers’ rights ↗ · ACAS: checking holiday entitlement ↗ · Related guide: holiday pay records →
Check access—not just the written policy
A policy can look neutral while its operation excludes part-time staff. Training always held on a non-working day, promotion briefings shared only in one meeting or a bonus requiring weekday attendance can create a disadvantage.
Consider a part-time administrator in Stockton who works Monday to Wednesday. If essential system training is scheduled every Thursday, simply saying that the course is open to everyone does not provide meaningful access. The manager should consider another session, paid attendance by agreement, recorded material or another effective arrangement. The solution should fit the training and role, not create a promise that every event will suit every pattern.
Review pensions, enhanced family and sick pay, health benefits, career breaks, vacancy communications and development programmes. Check payroll and HR systems too: a correctly worded handbook will not fix an hours threshold embedded in a benefits portal.
Audit the rule, the system and the practical access.
HR + SAFETY can review part-time terms, benefits and manager practices, then identify where an hours rule needs evidence, adjustment or clearer documentation.
Discuss a part-time worker reviewKeep redundancy selection focused on the work
Part-time status should not be a shortcut for redundancy selection. ACAS and GOV.UK both identify redundancy selection and pay as areas protected by equal-treatment rules. A criterion that favours people who can work every weekday or that scores total output without adjusting for contracted hours may disadvantage part-time staff.
Define the genuine future staffing requirement, use an appropriate selection pool and test each criterion for relevance and impact. Compare performance rates or quality rather than volume that reflects longer hours. If the future role needs particular coverage, explain why and consider whether it can be achieved without excluding part-time workers.
Redundancy pay should also be calculated using the employee’s lawful weekly pay and complete continuous service. Part-time service is not worth fewer years. Keep the equality check alongside the business case, consultation record and scoring evidence.
Objective justification needs evidence
Different treatment can be lawful where the employer objectively justifies it. GOV.UK describes this as showing a good reason. In practice, identify the legitimate business objective, show how the difference helps achieve it and consider whether a less disadvantageous alternative would work. Convenience, habit or an untested assumption about cost is weak reasoning.
For example, an employer might argue that extending an insured benefit to very low-hours workers is disproportionately expensive. Before excluding them, obtain the actual cost, check the insurer’s terms and consider alternatives such as a proportionate employer contribution.
Part-time treatment can also overlap with indirect sex discrimination. ACAS notes that women are generally more likely to work part time. A universal hours rule that particularly disadvantages women may therefore require separate analysis under the Equality Act 2010, with its own legal test. Passing one assessment does not automatically answer the other.
Part-time worker equal-treatment checklist
A part-time worker who believes they have been treated less favourably may request a written statement of reasons. The request should be in writing and the employer must respond within 21 days. Treat the response as a factual explanation supported by records—not a defensive formula produced after the event.
Legal requirements and official guidance were checked on 26 September 2026. Individual cases can also involve contractual terms, employment status, discrimination, family leave or collective arrangements, so obtain advice where the proposed difference is material or disputed.
- List each pay, benefit, leave, training, promotion and redundancy rule that could operate differently by hours.
- Identify an actual full-time comparator with the same employer and contract type doing the same or broadly similar work.
- Compare hourly rates and access before applying any pro-rata calculation.
- Check contractual and discretionary bonuses, pensions, sick pay and family-related benefits.
- Calculate holiday in a way that preserves the equivalent entitlement in weeks.
- Test whether training and opportunities are genuinely accessible across working patterns.
- Review redundancy pools, criteria, scores and payments for hours-based disadvantage.
- Document the legitimate aim, evidence and alternatives where relying on objective justification.
- Check whether an hours rule could also create indirect discrimination.
- Answer a written request for reasons within 21 days and preserve the decision record.
- Correct payroll, policy and system settings where the practical treatment does not match the written rule.
Different hours can justify a proportionate amount; they do not justify lower status. Identify the correct comparator, compare each treatment, use pro rata carefully and keep evidence for any objective justification.
This guide provides general information for UK employers. It is not legal advice and should not replace advice based on the facts of a specific matter.