As stated in the Programme Manual, section III.A.v.b, “Expenditure related to the implementation of the project and to closure activities, must be paid by the ending date of the project. In order to facilitate the closure process, the Programme recommends to complete the activities related to the implementation of the activities 3 months before the end date of the project”.
To do so, it is recommended to plan as end date of the last project activities the last month of the project, but to plan to deliver the related deliverables about 3 months before the ending date. All expenditure related to the implementation and closing activities must be paid by the ending date of the project.
Concerning the implementation period, please consult as well the FAQ: https://interreg-euro-med.eu/en/faq-document/is-the-duration-of-the-closure-period-included-in-the-total-duration-of-the-project-already-set-how-long-shall-it-be/