When you have a U.S. spouse, you can apply for U.S. citizenship in three years instead of the standard five years.The five-year rule does not require this “living in marital union” portion. Importantly, you and your U.S. spouse must remain married until the applicant naturalizes, but the “living in marital union” requirement is only required until the time of filing.

Other Requirements:-

1- You must submit federal tax returns for either three or five years, depending on which rule you are applying.

2- Never register to vote or claim to be a U.S. citizen on any paperwork before being naturalized.

3- Green card holders may hold permanent residency in the United States but are not safe from deportation if they commit certain crimes.

Procedure:-

1- Fill out and submit Form N-400 (officially called the “Application for Naturalization”) along with all required additional documentation.

2- The second step is to attend a biometrics appointment, where USCIS will process your fingerprints, photo, and signature.

3- After this, you will receive a notice with a date, time, and location for your U.S. citizenship interview. At your interview, you will be placed under oath and asked to take an English and civics test (unless you qualify for an exemption or waiver).

4- As part of the interview, the USCIS officer will ask you questions about your application and determine your eligibility for U.S. citizenship. If applying under the three-year rule, you may face questions and scrutiny over whether you have a bona fide marriage and genuinely “lived in a marital union.”

5- The final step on your citizenship journey is taking the Oath of Allegiance. In some locations, the oath is administered on the same day as your interview, but usually, you have to make an appointment to come back for it at a later stage to a USCIS field office.

Yes they can apply for citizenship after three years instead of 5, provided they meet some requirements.