Tensioning system (1, 101, 201, 301) for tensioning a fixing element (2, 102, 202, 302), wherein the tensioning system (1, 101, 201, 301) comprises the fixing element (2, 102, 202, 302), a deformation element (3, 103, 203, 303) and a mounting tool (4, 104, 204), wherein the fixing element (2, 102, 202, 302) has a tensioning element (12, 112, 212, 312) having a tool seat (14, 114, 214, 314) for connection to the mounting tool (4, 104, 204) for conjoint rotation therewith, especially a nut or a screw head having flats, so that for tensioning of the fixing element (2, 102, 202, 302) the tensioning element (12, 112, 212, 312) can be rotated with the mounting tool (4, 104, 204) about a longitudinal axis of the fixing element (2, 102, 202, 302) and at the same time the deformation element (3, 103, 203, 303) can be compressed under the action of a tensioning force from a starting height (h 0) in an undeformed pre-mounting position to a final mounted height (h E) in a final mounted position, characterised in that the tensioning system (1, 101, 201, 301) has a stop (21, 121, 221) against which or with which the mounting tool (4, 104, 204) bears during tensioning in such a way that the stop (21, 121, 221) limits axial movement of the mounting tool (4, 104, 204); and during the compression of the deformation element (3, 103, 203, 303) to the final mounted height (h E), the tensioning element (12, 112, 212, 312) is released by its tool seat (14, 114, 214, 314) from its conjointly rotating connection with the mounting tool (4, 104, 204) so that, once the final mounted position has been reached, the mounting tool (4, 104, 204) and the tensioning element (12, 112, 212, 312) are no longer connected for conjoint rotation. wherein the tensioning system (1, 101, 201, 301) comprises the fixing element (2, 102, 202, 302), a deformation element (3, 103, 203, 303) and a mounting tool (4, 104, 204), wherein the fixing element (2, 102, 202, 302) has a tensioning element (12, 112, 212, 312) having a tool seat (14, 114, 214, 314) for connection to the mounting tool (4, 104, 204) for conjoint rotation therewith, especially a nut or a screw head having flats, so that for tensioning of the fixing element (2, 102, 202, 302) the tensioning element (12, 112, 212, 312) can be rotated with the mounting tool (4, 104, 204) about a longitudinal axis of the fixing element (2, 102, 202, 302) and at the same time the deformation element (3, 103, 203, 303) can be compressed under the action of a tensioning force from a starting height (h 0) in an undeformed pre-mounting position to a final mounted height (h E) in a final mounted position, characterised in that the tensioning system (1, 101, 201, 301) has a stop (21, 121, 221) against which or with which the mounting tool (4, 104, 204) bears during tensioning in such a way that the stop (21, 121, 221) limits axial movement of the mounting tool (4, 104, 204); and during the compression of the deformation element (3, 103, 203, 303) to the final mounted height (h E), the tensioning element (12, 112, 212, 312) is released by its tool seat (14, 114, 214, 314) from its conjointly rotating connection with the mounting tool (4, 104, 204) so that, once the final mounted position has been reached, the mounting tool (4, 104, 204) and the tensioning element (12, 112, 212, 312) are no longer connected for conjoint rotation.