A photomask having a machine-readable identifying mark and suitable for manufacturing integrated circuit devices and a method for forming the photomask and identifying mark are disclosed. An exemplary embodiment includes receiving a design layout corresponding to a pattern to be formed on a photomask blank. A specification of an identifying code is also received along with the photomask blank, which includes a substrate, a reflective layer, and an absorptive layer. A first patterning is performed using the design layout. A second patterning is performed using the specification of the identifying code.