Some of the requirements for getting citizenship in the U.S. involve proving your personal ties to the U.S. through your residence and presence. Also, you will need to undergo your biometrics appointment and your naturalization interview in the U.S., and your naturalization oath ceremony will happen in the U.S. If you leave the country before these stages of the process happen, you will need to return to complete them.
You also will need to show that you have not abandoned your permanent residence in the U.S. as a green card holder. The clearest type of abandonment involves moving to a foreign country with the intent to set up a permanent residence there. Abandonment also can be inferred if a green card holder stayed outside the U.S. for an extended period. If you spent more than six months outside the U.S. at one time, USCIS may question whether you have abandoned your permanent residence. If your trip lasted more than a year, you may face an uphill battle in proving that you did not abandon your residence in the U.S. unless you can show that you had a compelling reason to be gone for such a long time and that you maintained your ties to the U.S. during that period. If you are constantly traveling outside the U.S., such that you spend very little time in the U.S. each year, this also may lead to abandonment.
The Continuous Residence Requirement
In most cases, you must have five years of continuous residence in the U.S. before you apply for citizenship and before the naturalization oath ceremony. There are some exceptions, especially for foreign nationals who are married to a U.S. citizen. (Read more here about the residency requirement and exceptions to it.) Your permanent residence must have remained in the U.S. during this period. Living in a foreign country during part of the period does not defeat the continuous residence requirement, as long as you continued to believe that the U.S. was your home and planned to return.
As with the abandonment issue, an absence of more than six months will raise red flags. USCIS will presume that you did not have continuous residence during this period unless you can prove certain facts. You can defeat the presumption by showing that your employment remained in the U.S., your family members remained in the U.S., you did not abandon your home in the U.S., and in general you continued to act as though the U.S. was your home.
An absence of one year or longer creates a gap in continuous residence, regardless of any evidence that you can produce. This automatically requires a foreign national to restart the continuous residence period. You must wait four years and a day before applying again for citizenship (or two years and a day if the three-year exception applies).
The Physical Presence Requirement
In addition to continuous residence for five (or possibly three) years, you must show that you were physically present in the U.S. for half of that period. USCIS will count the total number of days that you spent in the U.S. during the five-year (or three-year) period. This is a situation in which taking many short trips outside the U.S. could cause a problem, even if you did not take any trip that lasted more than six months. Days on which you left for trips or returned from trips will count as days of physical presence.
In addition, you must meet a more specific requirement related to the time during which you have lived in your state or USCIS service district. You must have spent at least three months in your state or service district before applying for citizenship. Your interview and naturalization oath ceremony will occur in this location, unless you request permission to change the location. However, if you are returning to your pre-existing home in the U.S. after spending a year or less outside the country, you can apply for citizenship immediately if you had lived in that state or service district for at least three months before your trip.
A foreign national who is attending a college or another educational institution outside the state where they live can apply for citizenship in the state where their school is located. If they depend on their parents for financial support throughout the application process, they can apply in the state where their parents live.