When a person applies for lawful permanent resident status (either within the US or from abroad) their past presence in the US is considered.  If a person was in the United States without legal immigration status for a period of 6 months or longer, and then left the country, he or she may be subject to a bar from admission.  If a person departs the US after a period of 6 months to 1 year unlawful presence they cannot be admitted as an LPR for at least 3 years.  If a person departs the US after a period of unlawful presence lasting 1 year or more, they cannot be admitted as an LPR for at least 10 years.  People in this situation may be able to apply for a waiver of these bars if they have a qualifying relative (a spouse or parent who is a US citizen or LPR) who will suffer “extreme hardship” without the immigrant family member.  This waiver is submitted on Form I-601 and requires documentation of the suffering of the qualifying relative.