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The principles of the relationship between the employee and the employer are freely determined within the framework of the provisions of individual or collective labour agreements, provided that they do not violate the mandatory legal rules in the legislation. In addition to contracts, employers can create various internal regulations and workplace practices in order to create suitable working conditions and order in the workplace.  Workplace application is the habitual, de facto behaviour that the employer continuously provides an interest on his own initiative and under the same conditions. Workplace practices regulated by the employer in accordance with the first paragraph of Article 22 of the Labour Law No. 4857 ("Labour Law") are considered as annexes to employment contracts. As an example of frequently encountered workplace applications today; The premiums and bonuses provided to the workers, additional social benefits such as housing, clothing and fuel aid and other financial benefits and longer annual leave with the pay periods regulated in the law.
With the implied acceptance of the employer's actual behaviour that provides benefits to the workers, the conditions under which the workplace practice will be accepted and included in the content of the employment contract has not been clearly determined by the legislator, and the evaluation criteria are shown in the established case law of the Court of Cassation.  If the criteria are found in a present case, these behaviours of the employer will be considered as workplace practice and will be considered as a provision of the employment contract between the parties. In the evaluation to be made, it will be examined whether the employer creates a justified expectation in accordance with the rule of honesty as a result of the employer's actual behaviour, rather than whether the employer thinks or wants to be binding in the future while performing this actual behaviour.
In order to determine whether a workplace practice is to be considered as an annex of the employment contract between the parties, the criteria determined by the Court of Cassation should be examined:
- The first factor to be considered at this point is that the act performed by the employer is of a general nature to be applied to all workers or a certain part of the workers in the workplace. Thus, the employer will create general and uniform working conditions in all or part of the workplace. The various benefits that the employer unilaterally grants to workers of different qualifications individually can be considered as an implicit provision of the employment contract of these persons, but cannot be interpreted as a workplace practice due to their lack of general nature.
- Another criterion taken into consideration is that the said practice is repeated for a certain period of time and constitutes continuity.  There is no exact measure for the acquisition of continuity, and it is observed that the decisions of the Court of Cassation on this issue vary.  In order to be evaluated as a workplace practice, "according to the nature of the event, there should be enough time for workers to deduce that the practice has become a habitual behavior in the workplace and that it will be done in the future." 
- Another element sought for workplace practices in the decisions of the Court of Cassation is the provision of the act under the same conditions. The employer's repetition of payments and benefits, which are based on the same reason as this criteria, and have some changes in terms of quantity or quality, will constitute the basis for a continuous workplace practice. In cases where the amount of the performance is not determined precisely, the amount will be determined in fairness.  In the concrete case, if there is consistency in terms of the amount and quality of the interest, it will be accepted that the workplace application is formed on the same amount and quality or it will be determined according to the same calculation method. In case of deficiency, workers will be able to demand the full rights of the workplace practice. In case the benefit to be provided to the workers is only due to the realisation of a certain condition, it will be possible to evaluate an application that continues over the years as a workplace application and the workers will be entitled to the benefit when the condition is fulfilled.
In the presence of the criteria that are shaped by the established jurisprudence of the Court of Cassation and discussed above, the workplace practice in question; Pursuant to Article 22 of the Labour Law, major changes against the employee, which will become one of the working conditions and will be made by the employer, can only be made with the written consent of the worker. As a matter of fact, it has become a working condition in the decisions of the Supreme Court on this subject, and it is stipulated that any workplace practice that creates benefits for the workers can only be changed or removed with the written consent of the worker.  Examples could be; cases where unilateral benefits to be provided by the employer to the workers for a certain period of time do not constitute workplace practice; cases where the employer reserves the right to give up while the relevant benefit is provided to the workers and the rights given to the workers as a result of error.
As a result, workplace applications emerge as a complementary resource. These practices, which were carried out unilaterally by the employer at the beginning and are not binding, will be included in the content of the employment contract when certain conditions are met, so that the employer will not be able to return unilaterally from these practices.
 Court of Cassation 7.HD, E. 2015/43401, K. 2016/6392, T. 16/03/2016
 Court of Cassation 9.HD, E. 2010/22802, K. 2012/41757, T. 06/12/2012
 Court of Cassation HGK, E. 2003/11, K. 2003/54, T. 05.02.2003
 Court of Cassation9.HD, E.2002/14254, K. 2003/2020, T. 20.02.2003
 S. Süzek, İş Hukuku, 15. Baskı, İstanbul 2018, s. 84
 P. Soyer, Genel İş Koşulları, İzmir 1987, s. 43-44
 Court of Cassation 9.HD, E. 2008/34000, K. 2008/35532, T. 26/12/2008