Under the Immigration and Nationality Act, if an individual is in the United States for more than 180 days but less than one year unlawfully and departs, he or she cannot return for a period of five years. If an individual has accrued one year or more of unlawful presence and leaves the country, he or she is barred from returning for a period of ten years. An individual, who has accrued over one year of unlawful presence, and who departs and reenters or attempts to reenter without admission or parole is inadmissible until he or she has resided outside the United States for ten years and then receives a waiver from the Department of Homeland Security (DHS) to apply for a visa to return to the United States. There are exceptions, tolling, and waivers for what are known as the three and ten-year bars. Periods of time in unlawful presence prior to April 1, 1997 are not counted. It is important to note that although the unlawful presence accrues while the individual is in the United Sates, the bars to admissibility do not attach until he or she leaves the United States and seeks to reenter.

An individual is deemed to be unlawfully present in the United States if he or she is present after the expiration of an authorized period of stay or is present without being admitted or paroled. The following categories of individuals are considered to be in an authorized period of stay: conditional permanent residents, parolees, nonimmigrants with an unexpired or duration of status I-94 card, adjustment of status applicants, and individuals granted voluntary departure as long as it has not expired. Additionally, certain periods of time cannot be counted towards unlawful presence. These include the following: periods of time when an individual was under 18 years of age; periods of time during which a bona fide application for asylum is pending unless the individual works without permission; periods of time during which the individual is a beneficiary of family unity protection under the Immigration and Nationality Act; periods of time spent in violation of the terms of their nonimmigrant visas by battered individuals and children if they can show a substantial connection between the battery and the unlawful status; and, where an individual can demonstrate that he or she was a victim of a severe form of trafficking which is at least one central reason for his or her unlawful presence in the United States.

The government may grant a waiver of the three or ten-year bars in the case of an immigrant who is the spouse, son, or daughter of a U.S. citizen or lawful permanent resident (LPR) if he or she can establish that the refusal of admission would result in extreme hardship to the qualifying relative. There is no waiver available to parents of U.S. citizens. Factors that are considered in determining whether an individual has established extreme hardship include: health; financial considerations; education; personal considerations; and other special factors. These special factors include: cultural, language and ethnic obstacles; fears of persecution, physical harm or injury; social ostracism; and access to social institutions and structures.