The law requires virtually all male U.S. citizens (regardless of where they live), and male immigrants residing in the U.S. (permanent resident aliens), to register within 30 days of their 18th birthday. Therefore, to be in full compliance with the law, a man turning 18 should register during the period of time beginning 30 days before, until 30 days after his 18th birthday...a 60-day window.



Late registrations are accepted, but not once a man reaches age 26. Men who do not register within the 60-day window are technically in violation of the law and should register as soon as possible.