A closure system comprising - a pourer equipped with non-drip lip and an annular abutment groove (11.1) associated with mentioned non-drip lip, - a cap having a flat top portion containing at least one circumferential projection (21.2) and a tubular portion which contains at least one security tab (22.1) corresponding to each circumferential projection (21.2) and at least one elastic flap (22.2) which is associated with each security tab (22.1) so as to bend - the security tabs (22.1) inward when the closure system is unscrewed from the bottle prior first opening and causing the tip of the security tabs to enter said annular abutment groove (11.1) when the closure system is unscrewed from the bottle after first opening, - an outer sleeve consisting of an upper sleeve portion, a tubular lower sleeve portion and a breaking line separating mentioned outer sleeve into two separate portions as upper sleeve portion and tubular lower sleeve portion, and characterized in that said outer sleeve is made of plastic and, in order to provide first opening guarantee to the end purchaser by allowing that mentioned circumferential projections (21.2) on the flat top portion of the cap deform permanently the top surface (31.1) of mentioned plastic upper sleeve portion after first unauthorized reclosing attempt of the closure system; mentioned closure system comprises - at least two circumferential indentations (31.3) located on the inner top surface (31.1) of the upper sleeve portion, as coinciding with the trajectory of said circumferential projection (21.2) portion located on the flat top portion of mentioned cap - at least one circumferential protrusion (31.4) located between each two consecutive ones of mentioned circumferential indentations (31.3), having the same wall thickness as the upper sleeve portion's top surface (31.1) wherein permanent deformation (31.5) on the top surface (31.1) of the said plastic upper sleeve portion via mentioned circumferential projections (21.2) occurs during a first unauthorized reclosing attempt executed by pressing on the upper sleeve portion, as highlighting whether mentioned closure system has been opened before. - a pourer equipped with non-drip lip and an annular abutment groove (11.1) associated with mentioned non-drip lip, - a cap having a flat top portion containing at least one circumferential projection (21.2) and a tubular portion which contains at least one security tab (22.1) corresponding to each circumferential projection (21.2) and at least one elastic flap (22.2) which is associated with each security tab (22.1) so as to bend - the security tabs (22.1) inward when the closure system is unscrewed from the bottle prior first opening and causing the tip of the security tabs to enter said annular abutment groove (11.1) when the closure system is unscrewed from the bottle after first opening, - an outer sleeve consisting of an upper sleeve portion, a tubular lower sleeve portion and a breaking line separating mentioned outer sleeve into two separate portions as upper sleeve portion and tubular lower sleeve portion, and characterized in that said outer sleeve is made of plastic and, in order to provide first opening guarantee to the end purchaser by allowing that mentioned circumferential projections (21.2) on the flat top portion of the cap deform permanently the top surface (31.1) of mentioned plastic upper sleeve portion after first unauthorized reclosing attempt of the closure system; mentioned closure system comprises - at least two circumferential indentations (31.3) located on the inner top surface (31.1) of the upper sleeve portion, as coinciding with the trajectory of said circumferential projection (21.2) portion located on the flat top portion of mentioned cap - at least one circumferential protrusion (31.4) located between each two consecutive ones of mentioned circumferential indentations (31.3), having the same wall thickness as the upper sleeve portion's top surface (31.1)