Attendance is not important for professionals! (This doesn't apply to unskilled positions or craft type positions- retail, manufacturing / etc.)
Focus on achievements and results, not what time the person showed up at his or her desk. Is the work getting done? Are they clients happy and continuing to do business with your company? Are goals being met? If you feel like that person has to be sitting at his or her desk at 8:00 AM sharp to produce results, maybe you need to replace that person, not write them up for not being at the desk at 8 AM. Hire competent people and let them do their jobs. Be their advocates and help them get the tools they need to be efficient and effective. Micro-management and clock-watching is not going to contribute to a successful organization.