The invention relates to an insert for a multilayer chip card, including an intermediate sheet and, on either side of the intermediate sheet, at least one outer sheet having a face in close contact with the corresponding face of the intermediate sheet, the intermediate sheet including at least one recess prior to the lamination of the insert. The insert having at least one of the outer sheets is made from a fluent material, such that, when the intermediate sheet is being laminated with the outer sheets, part of the material of the outer sheets moves into the recess in the intermediate sheet, thereby forming a visual and/or tactile defect on the surface of the insert, indicating whether of not the insert and/or the chip card is authentic.