Discipline for ‘forgetful’ clock-punchers: What are the limits?

Q: I have employees who routinely fail to punch in on the time clock. We then have to manually put their time in to the software. It seems to be happening with the employees who are late for work; they “forget” to punch in and then tell us to punch them in at the time they were scheduled. What can I legally do when they “forget” to punch in and then want to be punched in for a time that I know they weren't here? I obviously can't sit at the time clock and watch when everyone gets here.  -- Aubri, Michigan