Three year rule
A common question about immigration law is, “when can I file for citizenship.” Before you can apply for U.S. citizenship under the immigration law with U.S. Citizenship and Immigration Services – USCIS (formerly INS), you must first have a green card or permanent residence. If you received your green card through marriage to a U.S. citizen, you may be able to apply for citizenship through naturalization after having your green card for three years. In all other situations, you must wait five years.
How do I know if I can apply under the three year rule?
You must be married to a U.S. citizen.
You must be a lawful permanent resident – green card holder.
You must have resided continuously within the United States for a period of at least three years after having received permanent residence.
You must have been “living in marital union” with the citizen spouse for the three years immediately preceding the date of examination on the application, and your spouse has been a United States citizen for the duration of that three year period.
A divorce, legal separation, or even an informal separation may signify dissolution of the marital union. “Living in marital union” has been interpreted to mean actually residing together. Although the applicant is not required to live with the USC spouse after filing the application, they still must be married at the time of naturalization. But for all practical purposes, if you are not living with your spouse at the time of the naturalization interview, USCIS will highly scrutinize your eligibility.
You must have been physically present in the United States for periods totaling at least 18 months.
You have must have resided for at least 3 months immediately preceding the filing of the application in the State or Immigration district having jurisdiction over your application.
You must maintain your residence within the United States from the date of application for naturalization until the time of citizenship.
For all relevant periods during this process, you must be a “person of good moral character.” This essentially means that you cannot have a criminal history.
Once you have meet these criteria, you will need to file the proper immigration form N-400 and attend an immigration interview to take the U.S. Citizenship Test.