1. Once you receive a recommendation for post-completion OPT from your Designated School Official (DSO) to pursue OPT, you must apply for an employment authorization document (EAD) with USCIS within 30 days. Additionally, you may file up to 90 days prior to your program end-date and not later than 60 days after your program end date.
2. If you have completed a qualifying Science, Technology, Engineering or Mathematics (STEM) degree, and you are currently in an approved post-completion OPT period based on a designated STEM degree, you may be eligible to apply for a 17-month STEM extension of your post-completion OPT. For a STEM degree to qualify, it must appear on the STEM Designated Degree Program List. If you want to apply for a STEM extension, you must file for an extension of your EAD with USCIS before your current OPT work authorization expires. USCIS recommends that you file 90 days before the expiration of your OPT.
For further information visit the USCIS page on F-1 OPT requirements