Part-time workers make up a significant proportion of the UK workforce, yet their rights are frequently misunderstood — or worse, overlooked. The Part-Time Workers (Prevention of Less Favourable Treatment) Regulations 2000 give part-time employees the legal right to be treated no less favourably than comparable full-time colleagues. This guide explains what that means in practice and how employers can stay compliant.
The Part-Time Workers (Prevention of Less Favourable Treatment) Regulations 2000 (often called the PTW Regulations) are the cornerstone of part-time worker protection in the UK. The core principle is simple: a part-time worker must not be treated less favourably than a comparable full-time worker, unless the employer can objectively justify the difference.
The Regulations apply to all workers — not just employees. This includes agency workers, casual workers, and those on zero-hours contracts who work fewer hours than a comparable full-time colleague.
"Less favourable treatment" covers every aspect of the employment relationship, including:
For a part-time worker to bring a claim of less favourable treatment, they must identify a comparable full-time worker. The comparator must:
If no comparable full-time worker exists, the Regulations do not apply. However, employers should still aim for fair treatment to avoid broader discrimination claims.
Part-time workers are entitled to the same 5.6 weeks of statutory annual leave as full-time workers — but expressed pro rata based on the number of days they work per week.
Pro-rata leave = 5.6 × Days worked per week
Example: An employee working 3 days per week is entitled to 5.6 × 3 = 16.8 days of annual leave per year.
For employees with irregular hours or those who work different days each week, the calculation should be based on hours rather than days. Convert the full-time entitlement to hours and then apply the pro-rata fraction.
For a detailed walkthrough, see our pro-rata annual leave calculator guide.
Free Pro Rata Leave Calculator
Quickly calculate pro rata annual leave for part-time employees based on their working pattern.
Try it nowBank holidays are one of the most common sources of confusion — and complaints — when it comes to part-time workers. There are two key points:
If full-time employees receive the 8 bank holidays on top of their 20 days of basic leave (totalling 28 days), then part-time workers must receive a pro-rata share of the full 28 days. You cannot simply give part-timers the basic 20 days pro rata and then only grant bank holidays that fall on their working day.
If a bank holiday falls on a day the part-time worker does not work, they are still entitled to the pro-rata benefit. The simplest approach is to include bank holidays within the total leave entitlement and let the employee use them flexibly. For example:
This method is recommended by ACAS and avoids the unfairness of part-time workers who happen to work on Mondays (when most bank holidays fall) getting fewer discretionary leave days.
Even well-intentioned employers can inadvertently discriminate against part-time workers. Watch out for these common pitfalls:
| Area | What goes wrong | What the law requires |
|---|---|---|
| Training | Training sessions only scheduled on days the part-timer doesn't work. | Equal access to training. Offer alternative dates or adjust the schedule. |
| Promotion | Part-time workers overlooked for promotion because they are "not fully committed". | Promotion decisions must be based on merit, not hours worked. |
| Redundancy | Part-time roles selected for redundancy first, or part-time workers scored lower because of hours. | Redundancy selection criteria must not disadvantage part-timers. |
| Overtime | Part-timers paid at a lower rate for hours above their contract but below full-time hours. | Overtime premiums should apply at the same threshold as for full-time workers. |
| Pension | Part-time workers excluded from pension schemes or given a lower employer contribution. | Same pension access and contribution rate on a pro-rata basis. |
| Benefits | Part-timers excluded from company perks like gym memberships or health insurance. | Same access to benefits, pro rata where appropriate. |
If a part-time worker believes they are being treated less favourably, they have the right to request a written statement of reasons from their employer. The employer must respond within 21 days.
If the employer fails to respond, or provides an evasive or equivocal response, a tribunal may draw an adverse inference — in other words, it may assume that the less favourable treatment was because of the worker's part-time status.
Best practice: if a part-time worker raises concerns about unequal treatment, take it seriously and investigate promptly. Document your reasoning and any objective justification for any differences in treatment.
An employer can treat a part-time worker differently if the treatment is objectively justified. This means the employer must show that the less favourable treatment:
This is a high bar. "It's always been done this way" or "it's too complicated to change" will not satisfy a tribunal. Employers should document their justification thoroughly.
Calculating pro-rata leave, managing bank holiday entitlements, and ensuring equal treatment is one of the most error-prone areas of HR administration. Leavely automates it all: