A container with a permanent closure having a box body (2) and a cover (3), which are configured to interlock with each other in an indissoluble way; wherein the box body (2) comprises a collar (8) of polygonal shape with rounded corners having both straight sides and corners which connect two adjacent straight sides to each other; wherein the collar (8) is integral, in other words it has no through openings, in correspondence of the corners; wherein the collar (8) of the box body (2) comprises a projecting part (15) disposed in correspondence of a respective corner (11); wherein the projecting part (15) and the flap (24) are configured to form an interference coupling.