A closing cap for a container , comprising a lateral wall extending around an axis (Z) and a transversal wall positioned at one end of the lateral wall , a separation line being provided on the lateral wall to define: - a retaining ring , which is configured to remain anchored to a neck of the container and extends as far as a free edge ; - a closing element removably engageable with the neck , so as to open or close the container ; wherein - the separation line extends about the axis (Z) and is circumferentially interrupted to form in the lateral wall a joining zone , which extends for a first angle (α), in which the retaining ring and the closing element are joined; wherein the cap comprises - a tab , made in the joining zone , which extends circumferentially for a second angle (β) and is connected to the joining zone ; characterized in that the retaining ring comprises: - a retaining portion and a free portion , wherein the retaining portion comprises an engagement element configured to engage internally with a locking ring of the neck during a passage from a closed condition to an open condition of the closing element , and wherein the free portion comprises a movement element which extends circumferentially at least in the second angle (β) and is configured, during said passage, to allow a movement of the free portion along an axis parallel to the axis (Z); - wherein the tab is connected to the joining zone by a hinge zone , about which the tab may optionally bend and comprises a bottom edge , which is positioned on the opposite side relative to the hinge zone and is interposed between the hinge zone and the free edge of the retaining ring , and a pair of lateral edges , which extend from the hinge zone , the lateral edges being transversal to the bottom edge ; - wherein the tab comprises an outer part , made in the retaining ring and an inner part , made in the closing element , which are separated respectively from the retaining ring and from the closing element by respective stretches of the lateral edges . - a retaining ring , which is configured to remain anchored to a neck of the container and extends as far as a free edge ; - a closing element removably engageable with the neck , so as to open or close the container ; wherein - the separation line extends about the axis (Z) and is circumferentially interrupted to form in the lateral wall a joining zone , which extends for a first angle (α), in which the retaining ring and the closing element are joined; wherein the cap comprises - a tab , made in the joining zone , which extends circumferentially for a second angle (β) and is connected to the joining zone ; characterized in that the retaining ring comprises: - a retaining portion and a free portion , wherein the retaining portion comprises an engagement element configured to engage internally with a locking ring of the neck during a passage from a closed condition to an open condition of the closing element , and wherein the free portion comprises a movement element which extends circumferentially at least in the second angle (β) and is configured, during said passage, to allow a movement of the free portion along an axis parallel to the axis (Z); - wherein the tab is connected to the joining zone by a hinge zone , about which the tab may optionally bend and comprises a bottom edge , which is positioned on the opposite side relative to the hinge zone and is interposed between the hinge zone and the free edge of the retaining ring , and a pair of lateral edges , which extend from the hinge zone , the lateral edges being transversal to the bottom edge ; - wherein the tab comprises an outer part , made in the retaining ring and an inner part , made in the closing element , which are separated respectively from the retaining ring and from the closing element by respective stretches of the lateral edges . <EOS>