UK part-time employment: hours, rights, compliance

In the UK labour market, part-time work stands out as the model that offers workers flexibility and helps employers adapt to staffing needs. But it often gives rise to various questions. How many hours is part-time? What rights do part-time workers have? How can HR stay compliant with UK law?

This guide explains how part-time employment works in the UK, highlighting the essential points HR teams, employers and workers need to understand.

Key takeaways

  • There is no fixed legal number for part-time hours in the UK.
  • Part-time workers have the same statutory rights as full-time staff, on a pro rata (proportional) basis.
  • Misclassification can trigger tribunal claims, penalties and HMRC issues.
  • HR compliance requires accurate contracts, monitoring, and digital tools.

How is part-time work defined under UK law?

Official definition and legal working hour limits

The UK law does not provide a strict definition of how many hours count as part-time employment. Instead, the legal framework describes it as any role where the contracted hours are fewer than those of a comparable full-time worker. A full-time contract is usually 35–40 hours per week, so part-time hours fall below that threshold.

Working time regulations apply equally to all employees. A part-time worker is entitled to the same rest breaks, daily rest periods and limits on maximum working hours as full-time colleagues. Employers cannot reduce these protections simply because a worker is on a part-time contract.

Difference between part-time, full-time and compressed hours

In the most simple terms, part-time hours are fewer than full-time hours.

However, this is not the same as arrangements like compressed hours. With compressed hours, employees still work the same number of total hours as full-time staff, but across fewer days. For example, someone might work four longer days instead of five shorter ones.

Understanding this difference is critical for maintaining HR compliance. Compressed hours do not change statutory rights, annual leave calculations, or eligibility for employee benefits. By contrast, part-time work directly affects how pro rata entitlements are calculated.

Are part-time rules the same across all contracts?

Yes and no. Even though the law applies equally, individual contracts set the terms of work. Some part-time employees may work fixed weekly schedules, such as 20 hours over five days. Others may work irregular patterns or shifts. Actually, this often is the case in retail or hospitality. Employers must ensure contracts meet statutory rights and do not discriminate against part-timers.

How many hours per week is considered part-time in the UK?

Legal and practical thresholds

There is no single legal threshold for how many hours constitute part-time work. The UK law leaves flexibility. In practice, employers and HR teams often use markers such as 16, 20, or 30 hours per week. This type of flexible arrangement helps employees combine work with family, study or lifestyle needs.

Role of employment contracts and working patterns

The employment contract should clearly define working hours (whether fixed or flexible) and how pay and benefits will be applied. Ambiguous contracts increase the risk of tribunal claims if disputes arise about pay, holiday or pro rata entitlements. Contracts must:

  • State expected weekly hours.
  • Clarify whether hours are fixed, variable, or seasonal.
  • Outline pay and entitlements on a pro rata basis.

Flexible working arrangements can be combined with part-time contracts, but HR must ensure compliance with working time regulations and protect staff from excessive workloads.

Can employers set their own limits?

Employers may define what they consider full-time or part-time within reason. But they cannot set arbitrary rules that treat part-time workers unfairly or deny them rights. For example, refusing to allow part-time employees access to training, pensions, or bonuses would likely breach discrimination law and result in tribunal claims.

Part-time workers: pro-rata holiday calculation

Part-time staff are entitled to the same 5.6 weeks of annual leave as full-time employees.

Holiday entitlement is based on the days you normally work each week, not on the hours worked. If you usually work 3 days a week, then each “day of holiday” means one of your normal working days off, whether that day is 4 hours long or 10 hours long.

Formula:

5.6 × number of days worked per week = annual leave

Examples:

  • 3 days per week x 5.6 → 16.8 days holiday
  • 2 days x 5.6 → 11.2 days holiday

For staff on irregular hours or part-year contracts, holiday isn’t set as a fixed number of days. Instead, it accrues gradually based on the hours worked in each pay period. From April 2024 onwards, these workers must have their entitlement calculated through accrual, rather than by averaging their typical week. For accurate figures, use the official GOV.UK holiday entitlement calculator*.

What are the legal rights of part-time employees?

Breaks, rest time and maximum working hours

Break entitlements and daily rest periods are guaranteed under working time regulations, which form part of the wider workable hours rules in the UK. Part-time employees are entitled to the same rest breaks as full-time staff. Legally, employees are entitled to:

  • At least 20 minutes uninterrupted break for shifts over six hours.
  • 11 hours’ rest between shifts.
  • One day off each week.
  • Maximum of 48 hours per week averaged over 17 weeks (unless opted out).

Equal pay and non-discrimination versus full-time staff

The Part-Time Workers (Prevention of Less Favourable Treatment) Regulations 2000 ensure that part-timers receive equal treatment. They must receive the same hourly rate of pay, access to training, and opportunities for promotion as full-time colleagues. Non-compliance can lead to tribunal claims and reputational damage.

Holiday entitlement and sick pay

Holiday entitlement is based on the pro rata calculation. Sick pay is also applied on the same basis as full-time staff, provided the employee meets the earnings thresholds for statutory sick pay. Pension contributions must also be provided where part-time workers meet eligibility.

What are the risks of misclassifying part-time workers?

Legal penalties and employment tribunal cases

If employers misclassify part-time staff or deny them rights, they may face legal action. Employment tribunals can order back pay, compensation and penalties. HR compliance requires ongoing checks to avoid such risks. A recent example is King v Capital City College, where a part-time lecturer won over £30,000 after being denied pay and pension contributions for extra duties that full-time staff would have been compensated for.

Impact on tax, pensions and benefits

Incorrectly classifying hours can lead to underpaid pension contributions, inaccurate payslips or HMRC fines. This also affects employee benefits like occupational health support, redundancy rights and access to job-share schemes. Small slip-ups, like overlooking variable hours or misrecording attendance, can quickly cascade into compliance issues with costly financial and legal consequences.

HR audit: key indicators to review internally

Reviewing contracts annually reduces the risk of costly mistakes. A compliance checklist should review:

  1. Do contracts reflect actual hours worked?
  2. Are entitlements calculated pro rata?
  3. Is there equal access to training and promotions?
  4. Are pay slips accurate?
  5. Are records reviewed annually?

Checklist: 5 signs your part-time contracts may not be compliant

  1. No written contract or statement of particulars

 Employers must provide clear written terms covering hours, holiday and pay.

  1. Holiday, sick pay  or pensions not applied pro rata

 Entitlements must match full-time colleagues, adjusted pro rata.

  1. Inaccurate payslips or mis-stated hours

 Payslips must show correct hours, deductions and accruals.

  1. Working time regulations not applied

 Breaks, rest periods and weekly limits apply equally to part-timers.

  1. Part-time staff treated less favourably

 Part-time workers must get equal access to pay, training and promotions.

How can HR teams ensure compliance with part-time contracts?

Drafting accurate contracts and working-hour clauses

A well-drafted employment contract sets the foundation for compliance. HR teams should:

  • Define contracted hours and working patterns, including whether hours are fixed, variable or seasonal.
  • Clarify holiday pay and pro rata entitlements in writing.
  • Avoid vague wording such as “as required,” which can lead to disputes on overtime or scope of duties.

Monitoring hours vs actual attendance

Even the best contract is ineffective without proper monitoring. Compare contracted hours with actual attendance data to ensure staff are not regularly exceeding limits. Tools like time and attendance software make this easier by providing accurate, real-time records and alerts.

Identify unpaid overtime or patterns of additional shifts that suggest a de facto full-time role. Use reporting tools to confirm compliance with working time regulations and highlight anomalies early.

Using HR software for alerts and documentation

So far, we’ve identified several risks for HR teams: misclassifying part-time hours, overlooking pro rata entitlements and failing to keep accurate records. These problems often arise when organisations rely on manual processes, fragmented systems, paper files or spreadsheets. To reduce those risks, HR teams need a reliable digital solution.

Kelio’s HRIS solution is an excellent tool for documenting part-time employment properly in the UK. It helps HR teams by:

  • Automating pro rata calculations for holiday pay, sick leave and pension contributions, ensuring entitlements are always applied fairly.
  • Providing real-time attendance tracking so HR can spot if part-time employees are working beyond their contracted hours.
  • Flagging compliance risks with alerts when working time regulations are close to being breached.
  • Generating audit-ready documentation that demonstrates compliance.

For HR teams, this means less time chasing data across systems and more confidence that every part-time contract is being managed fairly and legally.

Client insight: “Kelio helped us avoid non-compliance by automating work hour monitoring.”

Tip: Remote and hybrid part-time work can be monitored with the same rigour as on-site roles, as Kelio’s system captures attendance and hours wherever staff are based.

Frequently asked questions

Kelio’s time and attendance software and HRIS solution simplifies full-time employment, boosts productivity and strengthens compliance. Discover the benefits for your business.

Contact us for a free demonstration 

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