If you are planning on traveling to the U.S., you should carefully consider the required duration of your stay prior to applying to the U.S. - obviously, if overstaying your visa is part of your travel plan, that’s not a very good place to start.
Overstaying your visa’s validity can lead to you facing some pretty serious consequences, particularly if you ever plan on visiting the U.S. again in the future. To avoid facing these kinds of issues, you need to carefully plan your trip in advance, and make sure you understand the conditions and limitations that come with the visa type for which you are considering applying. Some visas allow for more flexibility than others, and the consequences of overstaying can vary quite considerably depending on the initial purpose of your stay in the U.S.
Most U.S. visas and entry permits are handled through the respective foreign Embassies, which often delegate the practical aspects to local Consulates in countries where travel times to the capital city can be considerable.
If you ever overstay a U.S. visa, one of the risks is that you will no longer be able to apply through local Consulates, and will be forced to travel to the designated U.S. Embassy every time you need to apply for a visa. Depending on where you live, this can be a serious obstacle and is something you may want to keep in mind.
A vast majority of the visa cancellation cases we get to handle are due to people overlooking their visa expiry date, or ignoring the maximum duration of stay on their visa. Many visitor visas, for example, are multiple-entry and have a validity period of 10 years - however, the holder of the visa is not allowed to stay in the U.S. for more than 6 months at a time without exiting and re-entering.
Ignoring this rule often leads to visa cancellation, which means needing to apply for a new visa, which will prove more difficult to obtain if a previous visa cancellation has taken place.
If you are in the U.S., and during your stay, you want or need to engage in activities that you had not initially planned and that aren’t allowed under the visa you received, it is possible to adjust your status and change your visa type. This way, you can change a nonimmigrant visa type to another nonimmigrant visa or into an immigrant visa (if eligible), or extend the permitted duration of your stay.
The most important thing to consider is that you can only apply for an adjustment of status as long as your current visa is still valid - in other words, you lose the possibility of adjusting your status if you let your visa expire. However, if you do apply for an adjustment of status before your visa’s expiry date, you will be permitted to remain in the U.S. as long as your extension/adjustment of status is being processed.
If you are found to have overstayed your visa, you risk facing an entry ban; if you have overstayed your visa for less than 12 months after it expired, and you have left the U.S. on your own initiative before any removal proceedings were initiated, this travel ban will likely last for 3 years. If you overstayed for more than 12 months, this ban will probably last for 10 years.
If you have been deported or removal proceedings were started against you, you will find yourself in a much more complicated situation, where it is possible that you will never be able to receive a U.S. entry permit again.
To make a long story short, you really want to avoid getting deported. If you do happen to overstay your visa, make sure to seek counsel from an experienced professional and prepare to leave as soon as possible.