The thesis below refers to the definition of the terms laytime and demurrage as well as their usage in real situations in shipping. These terms are legal and always are included to a voyage charter of a vessel. Laytime is the available time that Charterer has to complete the loading and the discharging operation of the cargo. Laytime begins when the vessel has reached to her destination, she is in all respects ready to commence her operation and has tender a valid NOR. When laytime finishes, comes to the demurrage.Demurrage is the amount of money that the Charterer pays up to the Owner due to the delay of the vessel (in excess of laytime) and is often per day pro rata. Once a vessel is on demurrage, always is going to be on demurrage except may be if the charter party includes a exemption clause. After finishing the discharging operations and collecting all the supporting documents, the Owners send the claim to Charterers within time bar agreed and wait for their comments or agreement. The preparation of this claim must be fully supported by analytical documents and time sheets which can be provided by the vessel, the terminal or the port agent. Finally, we will study some cases for a better understanding of all the above.