Paid Leave and Part-Time Work: Proportional Reduction Prohibited by the Court of Cassation

In Allonnes, a suburb of Le Mans, an employee of the Caisse nationale d'assurance maladie des travailleurs salariés (CNAMTS) experienced a situation that may resonate with you: after obtaining permission to work half-time to balance family and professional life, she discovered that her conventional seniority leave — a bonus of days off linked to her seniority — was reduced by half. Five days became two and a half. Is this legal? The question deserves to be asked, as it affects thousands of part-time employees.

This decision of the Court of Cassation, handed down on 4 June 1987, answers clearly: no. The judges held that the extent of paid leave entitlements cannot be assessed in terms of hours of work. In other words, switching to part-time does not justify mechanically reducing the number of seniority leave days. A victory for employees, but also a headache for employers who must revise their calculations.

Whether you are a part-time employee, an employer, or simply curious to understand the rules of labour law, this article deciphers for you the reasoning of the judges, the practical consequences, and the reflexes to adopt to avoid disputes. We will also see how, in La Ferté-Bernard as elsewhere, this case law continues to apply.

The Facts: A Story That Happens Every Day

Mrs X has worked at CNAMTS for several years. As provided for by the national collective agreement for staff of social security bodies, she benefits from a conventional seniority leave: five additional days of leave per year, in addition to statutory paid leave. Relying on her seniority, she requests a switch to half-time, which is granted. But the employer, applying an internal circular, reduces her seniority leave proportionally: the five days become two and a half days, i.e., twenty hours converted into ten hours.

Mrs X contests this decision. She brings the matter before the conseil de prud'hommes (employment tribunal) of Le Mans, which rules in her favour. CNAMTS appeals to the Angers Court of Appeal, which upholds the judgment. The employer then appeals to the Court of Cassation, arguing that the reduction is justified by the half-time work. But the Court of Cassation dismisses the appeal and validates the reasoning of the lower courts.

The key point: the collective agreement provided for seniority leave in days, not hours. However, the employer had converted these days into hours to reduce them by half. The judges held that this conversion was contrary to Articles L. 223-1, L. 223-2 and L. 223-4 of the Labour Code (now Articles L. 3141-3 et seq.), which lay down the rules for paid leave based on months of actual work, not hours.

The Reasoning of the Court — Analysed

The Court of Cassation relies on the provisions of the Labour Code relating to paid leave. Article L. 223-1 (old) provides that any employee who has worked for at least one month with the same employer is entitled to paid leave, the duration of which is determined according to months of work or equivalent periods. Article L. 223-2 specifies that the duration of leave is two and a half working days per month of work, not exceeding thirty working days. Finally, Article L. 223-4 assimilates certain periods (such as sick leave) to actual work.

The judges deduce a fundamental principle: the extent of paid leave entitlements cannot be assessed in terms of hours of work. In other words, paid leave is a right attached to the employee's person, calculated in days or months, not in hours. Thus, when an employee switches to part-time, their statutory paid leave entitlement is indeed reduced proportionally (because they work fewer days in the month), but a conventional seniority leave fixed in days in the collective agreement cannot be converted into hours to be reduced.

The Court goes further: it condemns the employer for misinterpreting the texts, despite the circulars received from CNAMTS. It recalls that the employer is obliged to apply the law correctly, regardless of the instructions of the body to which it is affiliated. In this case, CNAMTS had itself issued a circular recommending proportional reduction, but this circular was contrary to the law.

In doing so, the Court confirms constant case law: switching to part-time cannot reduce acquired rights in respect of conventional leave, unless the collective agreement expressly provides otherwise. This is a protection for employees who reduce their working time.

What This Means for You — Practically

For part-time employees: if your collective agreement provides for seniority leave in days (e.g., 5 days after 10 years of seniority), this number of days remains the same even if you switch to 80%, 50% or 20% of working time. The employer cannot reduce it proportionally. If you are in this situation, check your payslips and claim the missing days, subject to a 3-year limitation period (Article L. 3245-1 of the Labour Code).

For employers: you must calculate conventional seniority leave in days, not hours. Converting into hours to apply a reduction is prohibited unless the collective agreement explicitly provides for it. In La Ferté-Bernard, a SME with 15 employees had to reimburse 12 days of leave to a part-time employee, equivalent to €2,400 in compensation, after an inspection by the labour inspectorate.

For real estate professionals (agencies, syndics) who employ part-time employees, this decision directly concerns you. Do not forget: statutory paid leave (5 weeks) is already proportionally reduced for part-time workers, but conventional seniority leave remains intact.

Four Tips to Avoid This Type of Dispute

• Check your collective agreement. Look for provisions relating to seniority leave. If the text refers to 'days' without mention of a reduction for part-time work, the number of days is fixed.
• Keep all your documents. Payslips, contract amendments, employer correspondence. In case of a dispute, these are your evidence.
• When switching to part-time, have a precise amendment signed. The employer must clearly state that seniority leave remains unchanged. If in doubt, seek advice from a lawyer.
• Do not hesitate to consult a specialist lawyer. A simple letter of formal notice may suffice to restore your rights without going to trial.

Further Reading: Related Case Law and Developments

This 1987 decision is part of a protective line for part-time employees. The Court of Cassation has since confirmed this principle in other rulings, notably in 1995 (No. 92-44.123): seniority leave cannot be reduced proportionally to working time, unless the collective agreement provides otherwise. More recently, in 2018 (No. 16-25.646), the judges extended this rule to seniority bonuses, holding that they cannot be reduced pro rata to working time.

The trend is therefore clear: benefits linked to seniority (leave, bonuses) are considered acquired rights that switching to part-time cannot call into question. This means employers must be particularly vigilant in drafting their collective agreements and employment contracts.

Summary and Next Steps

Here is a checklist of what to do if you are affected:

1. Identify the type of leave: statutory or conventional?
2. Check the wording of the collective agreement: does it refer to days or hours?
3. Check your payslips: was the number of seniority days reduced after switching to part-time?
4. If so, gather the evidence and write to the employer to claim the missing days (with a copy of the Court of Cassation decision).
5. If refused, bring the matter before the employment tribunal within 3 years.

Are you in a similar situation? A first 30-minute consultation with Maître Zakine (€45) can save you months of proceedings — and often much more. Book an appointment →