The use of annual holiday si one of the fundamental rights of workers and the aim of this paper is to show the right to use annual holiday,how it is determined an how it is calculated. First are explained the types of vacations to which the worker is entitled are explained, then how to determine the entitlement to annual holiday and carry over the annual holiday to the next calendar year. By the Constitution of the Republic of Croatia, every employee is entitled to weekly leave and paid annual holiday and cannot be waived. Annual holidays are an obligation of the employer, the purpose of which is to enable the worker to take a physical and mental break after prolonged uninterrupted work in order for the worker to renew his or her work abilities. Every worker is required to take vacation and cannot be renounced. There are different ways of determining the right to annual holiday, namely the right to a proportionate part of the holiday, the right to the entire vacation and the right to compensation for unused vacation.