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1. What is a Substantial Change of Working Conditions (Article 41 ET)
A substantial change in working conditions, as established in Article 41 of the Workers’ Statute, is a legal mechanism that allows an employer to implement significant changes in key aspects of an employment contract. These changes may affect the working hours, schedule, work distribution, and other essential elements, provided that they exceed legally established thresholds. It is essential for both employers and employees to understand which modifications are considered substantial and the legal protections available for workers.
2. Working Hours, Schedules, and Shifts: When is a Change Truly Substantial?
Changes in work hours, schedules, or the introduction of shifts are deemed substantial when they alter the basic structure of the agreed-upon working time. This includes shifts from continuous to split working hours or the introduction of rotational shifts. Recent case law in 2026 highlights that such modifications must follow the legal procedures to protect the worker’s right to stable working conditions.
3. The Supreme Court Ruling of May 20, 2026: Unilateral Change Clauses are Null
The Supreme Court ruling (STS 491/2026, dated May 20, 2026) marked a milestone in the interpretation of Article 41. The court declared null the contractual clauses that allow companies to unilaterally modify working hours and schedules “due to organizational or productive needs.” This ruling reinforces that contractual stipulations cannot undermine the guarantees provided by the Workers’ Statute. It also applies a literal and contra proferentem interpretation of the relevant civil code articles, ensuring that any ambiguity is resolved against the employer who drafted the clause.
4. Individual Modification: Minimum Fifteen-Day Notice and Written Communication
For individual modifications, it is mandatory that the employer provides a minimum notice of fifteen days, informing both the employee and their legal representatives in writing. This requirement ensures that the worker has sufficient time to evaluate the proposed change and consider the option to terminate the contract if the modifications are detrimental.
5. Collective Modification: Thresholds and Consultation Period
When the changes affect a significant number of employees, they are considered collective modifications. The thresholds vary according to the size of the company: 10 employees in companies with fewer than 100 workers, 10% of the workforce in companies with 100 to 300 workers, and 30 employees in companies with more than 300 workers. In addition, a consultation period of no more than fifteen days is required, during which the causes, the possibility of reducing the impact of the changes, and proposed mitigating measures must be discussed.
6. Your Three Options: Accept, Terminate with 20 Days per Year, or Contest
When faced with a substantial change to your working conditions, you have three choices:
- Accept the modification and adjust to the new conditions.
- Terminate your contract and claim an indemnity of 20 days’ salary per year worked (prorated for periods less than a year, up to a maximum of nine months).
- Contest the measure if you believe that your rights have been infringed or the legal procedures were not appropriately followed.
7. How to Contest: 20 Business Days and the Procedure Outlined in Article 138 of the LRJS
If you choose to contest the modification, note that there is a strict deadline of 20 business days from receiving the written notice to file a claim, as set out in Article 138 of Law 36/2011. The process is urgent and preferential. In individual cases, the resulting judgment generally cannot be appealed, except under specifically provided circumstances. For collective challenges, the process is managed as part of a collective dispute, pausing individual actions until the issue is resolved.
8. When to Apply Article 40 (Geographical Mobility) Instead of Article 41
Not all changes fall under Article 41. Article 40 of the Workers’ Statute is specifically intended for geographical mobility cases, which involve relocations or transfers that require a change of residence. It is essential to distinguish between these scenarios, as geographical mobility follows its own set of notice and compensation rules.
9. Foreign Workers: Impact on Residence and Work Permit Renewal
For foreign workers, modifications in working hours or schedules can directly affect the renewal of their residence and work permits. For example, a change from full-time to part-time work or a reduction in salary can reduce income and social security bases, thereby influencing the renewal process, family reunion applications, and the calculation of professional life. It is therefore essential to keep all written communications, recent payroll slips, and employment history reports.
10. A Guide for Companies and HR Departments: Proving the Cause and Notifying Correctly
For businesses, especially HR departments, following correct procedural steps is key when implementing substantial changes. This includes thoroughly substantiating the reasons behind the modification, whether due to organizational or production needs, and notifying the affected employees in writing. Failure to provide proper documentation or to follow the prescribed notification process might render the measure void, as recent jurisprudence has warned. Proper management of these procedures not only minimizes legal risks but also promotes transparency and trust within the organization.
11. Common Mistakes and Essential Documentation to Retain
Common mistakes in the application of substantial modifications include inadequate written notice, failure to meet the minimum notice period, neglecting to hold the mandatory consultation in collective cases, and lacking thorough documentation of the justifying cause. Both employers and employees should keep copies of all communications, reports, and payroll documents related to the change. This documentation will be critical in any future legal challenge or to defend the measure in court.
12. Frequently Asked Questions
This section addresses some of the most common questions:
- What changes are considered substantial? Changes that affect the working hours, schedule, time distribution, and, in some cases, remuneration or functions—provided they exceed the limits established by law.
- What is the deadline to contest a modification? Employees have 20 business days from receiving the written notice to file a claim.
- How does it affect a foreign worker? Modifications can impact the renewal of residence and work permits, thus it is essential to maintain complete documentation of the employment situation before and after the change.
This article provides an in-depth and practical overview of substantial modifications concerning working hours according to current legislation and recent case law. Remember, this information is general in nature and does not substitute for individualized legal advice.
If you require personalized advice or have specific questions regarding your case, do not hesitate to contact Fernanda Vargas via WhatsApp here or book your appointment through Calendly here.