It depends on the type of change

Not all schedule changes have the same legal treatment under Portuguese law.

Change within the schedule adaptability margin: if the contract provides that the employer can adapt the schedule within certain limits, the change can be made with 7 days' prior notice.

Significant change (e.g. day shift to night shift): this is a substantial change to working conditions. It requires negotiation with the employee. If the employee refuses and the company insists, there may be grounds for resignation with just cause on the employee's initiative — meaning the company pays compensation.

Introduction of work on rest days (Saturdays or Sundays): requires agreement with the employee. It cannot be imposed unilaterally unless the contract or collective agreement allows it.

The rules in practice

Give adequate advance notice. For minor changes, 7 days is the minimum. For substantial changes, more time is appropriate and legally safer.

Document everything in writing. If the employee accepts the new schedule, record it in an addendum to the contract or in a signed written communication.

If the employee refuses: do not force the change without consulting a labour lawyer. Unilateral imposition of a substantial schedule change can give the employee the right to terminate the contract with compensation.

This article is for informational purposes only and does not constitute legal advice. For specific situations, consult a lawyer specialising in employment law.