You have 120 days from a work injury to notify your employer how you injured yourself. To get benefits from day one, you must give notice within 21 days. Thus, if you give notice on day 20, you get benefits from day one. Notify your employer on day 22, and you get benefits from day 22 on. If you suffer an occupational disease, the date you must give notice runs from the date you knew, or should have known, that your condition is work related. If you suffer a repetitive work injury such as carpal tunnel syndrome, the 120 day deadline runs from the date you last worked at the job that was worsening your condition. So if your employer claims that you can't pursue a claim because you didn't give notice within "24 hours" or some other internal deadline, you may still pursue a claim if you meet the deadlines set by Pennsylvania law.