Being present in the United States without a valid visa is called “unlawful presence” and is a violation of U.S. immigration laws. A person can begin to accrue unlawful presence in two ways: (1) by staying in the U.S. past the expiration date of a valid status (i.e. “overstay”), or (2) by entering the U.S. without being inspected by an immigration official (i.e. “entry without inspection” or what is commonly called an illegal entry).
If you are unlawfully present for less than 180 days, you may still be eligible to adjust status or depart the U.S. without triggering the bar. However, if you have been unlawfully present for 180 days or more, but less than one year, you are subject to a three year bar from the U.S. This means that if you leave the United States, you will not be permitted to reenter for three years. If you have been unlawfully present for one year or more, that bar is raised to ten years. It is important to note that the bar does not take effect until you leave the United States, which means regardless of how long you are in the United States, you cannot start counting down the 3 or 10 years until the day you depart the U.S.
Unlawful presence is a serious issue as it can result in not only the 3/10 bar but also Removal/Deportation. There are various forms of relief that may be available to you if you are unlawfully present, such as a Hardship Waiver or Adjustment of Status under 245(i). If you are unlawfully present in the U.S., it is important that you consult immigration counsel immediately to determine whether there is relief available to you.