The present invention relates to an adjustment drive, in particular a tailgate drive, having a bearing cover (2.1') which has a bearing surface (2.1.5') for bearing a drive-output-side gearing arrangement (2), wherein the drive-output-side gearing arrangement is rotatable about a drive output axis (2.5), wherein the bearing surface is arranged concentrically around a bearing cover axis (2.1.6'), wherein on the bearing cover there is provided, on the drive input side, a gearing housing (5') for bearing a drive-input-side gearing arrangement (8) and / or a drive motor, wherein the bearing cover comprises a reference element (61.2) which is at a defined distance from the bearing cover axis and on which the gearing housing is arranged. The present invention also relates to an adjustment drive, in particular according to the invention, having the bearing cover and the drive-output-side gearing arrangement, wherein on the bearing cover there is provided, on the drive output side, a fastening component (3') for the fastening of the adjustment drive, wherein the bearing cover comprises a reference element (61.1) which is at a defined distance from the bearing cover axis and on which the fastening component is arranged.