The Federal Supreme Court (STF) validated the 12-hour workday followed by 36 hours of rest (12x36) when agreed by individual written agreement between employer and employee.

Before the Labor Reform (Law 13,467/17), this work schedule could only be adopted when provided for by law or by collective bargaining agreement, as set out in Precedent 444 of the Superior Labor Court (TST). However, the Labor Reform allowed for 12x36 working hours to be agreed by individual agreement, without the need for labor union participation.

As a result of this change, the National Confederation of Health Workers (CNTS) filed a Direct Action of Unconstitutionality (ADI 5994), arguing against the constitutionality of the rule in relation to the 12x36 working day. The organization argued that this practice would violate subsection XIII of article 7 of the Federal Constitution, which guarantees working hours of no more than 8 hours per day and 44 hours per week, with the possibility of offsetting working hours by collective bargaining agreement.

The discussion has been on the STF's agenda since April of 2021. The decision was issued on June 30, 2023, recognizing the constitutionality of the Labor Reform in this regard. Thus, based on workers' freedom, the STF validated that it is not necessary to negotiate with the labor union to apply the 12x36 work schedule.

Justice Marco Aurélio (reporting judge) voted to grant the action, on the understanding that the Constitution does not cover individual work agreements for the 12x36 work schedule. Justices Edson Fachin and Rosa Weber also voted in favor, with the same understanding.

However, the prevailing opinion was that of Justice Gilmar Mendes, on the grounds that the possibility of making an individual agreement is a prerogative of the worker's freedom, and the Constitution does not prevent the 12x36 work schedule, since the extra hours worked are offset with more rest time.

The Justice also pointed out that Precedent 444 of the TST provides for the legitimacy of the 12x36 work schedule, as long as it is provided for by law or collective bargaining agreement, and that the STF itself had already validated this work schedule for civilian firefighters (ADI 4842). The opinion was concurred with by Justices Dias Toffoli, Carmem Lúcia, Luís Roberto Barroso, Alexandre de Moraes, Nunes Marques, and Luiz Fux.

This decision is an important precedent and brings greater legal certainty to companies that have adopted this type of scale through individual agreements since the Labor Reform, reinforcing the guidelines for freedom of negotiation brought in by the legislation.