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U.S. Citizenship Requirements

Understanding the naturalization requirements for green card holders

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What are the requirements for U.S. citizenship?

In order to become a U.S. citizen, all naturalization applicants must meet the following requirements (unless they qualify for an exemption or apply based on their U.S. military service):

In the following sections, we’ll discuss each of the U.S. Citizenship requirements in greater detail. Boundless also has a detailed guide to U.S. citizenship to help you understand the entire process.

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Minimum Age

You must be at least 18 years old to apply for naturalization — unless you’re applying based on any period of wartime military service, in which case you may be any age. Our guide to becoming a naturalized citizen has more details about eligibility and exemptions.

Continuous and Physical Presence

Demonstrating “continuous presence”

You must have continuously lived in the United States as a green card holder for at least five years (or at least three years if you’re married to a U.S. citizen). “Continuously” means you did not take any trips outside of the United States that each lasted six months or longer during the 3–5 years you’re required to have a green card (plus the extra period while USCIS processes your U.S. citizenship application). In other words, you’re allowed to leave the United States — just make sure to return within six months every time.


If you leave the United States for more than six months as a green card holder, USCIS will presume that you abandoned your permanent residence in the United States, and they’ll deny your U.S. citizenship application.

There are ways to overcome that presumption even if you do take an extended trip abroad. The chance of success, however, depends on a few factors:

  • How long you stayed outside the United States
  • How compelling your reason was for not coming back sooner
  • The discretion of the USCIS officer evaluating your application (officers can still deny your application based on other reasons, including if you took frequent trips abroad)

Those applying for naturalization based on a certain period or type of military service do not need to meet this “continuous presence” requirement. See this eligibility chart to learn when certain military service members can apply for naturalization.

You may submit your naturalization application as early as 90 days before you actually finish waiting the required three or five years. Our guide to Form N-400 has more details.


To avoid being denied citizenship, you’ll need to convince the USCIS officer evaluating your application that you didn’t intend to abandon your permanent residence in the United States during the time you were abroad (for more than six months but less than one year).

To accomplish this, you’ll need to provide evidence that you maintained strong ties to the United States. This evidence could show, for example, that you:

  • Kept your job in the United States and didn’t seek employment while abroad
  • Have immediate family members who remained in the United States
  • Kept your home in the United States
  • Enrolled your children in a U.S. school


If you stayed abroad for one year or longer, USCIS will automatically assume you abandoned your permanent residence in the United States. They will deny your U.S. citizenship application, and you’ll have to wait before you can reapply:

  • If you had to wait five years to apply for citizenship, you’ll need to wait at least four years and one day upon returning from your trip abroad to reapply.
  • If you had to wait three years to apply for citizenship (as the spouse of a U.S. citizen), you’ll need to wait at least two years and one day upon returning from your trip abroad to reapply.


To avoid the presumption that you abandoned your permanent resident status, it’s important to take certain precautions prior to leaving the United States.

Here are your options:

1. Apply for a “re-entry permit.” If you anticipate needing to stay abroad for at least one year, it’s essential to apply for a “re-entry permit” (using Form I-131, officially called the “Application for Travel Document”) before you leave the United States.


Form I-131 is used to apply for both a re-entry permit and a typical travel permit. But these two permits — though both intended to allow the traveler to re-enter the United States upon returning from a trip abroad — are not the same: a re-entry permit is issued to current green card holders, whereas a travel permit is issued to green card applicants.

You’ll need to provide biometrics while you’re in the United States, but you can request to pick up your re-entry permit from the U.S. embassy or consulate in the country where you plan to visit (or ask for expedited processing if your trip is due to an emergency). The re-entry permit is valid for two years and cannot be extended, so you must return before the two years has concluded. Otherwise, you most likely won’t be allowed to re-enter the United States.

2. Apply for “preservation” of your permanent residence. You’ll be allowed to keep your permanent resident status if you must stay abroad for one year or longer because of your work, but it must be a specific type of work approved by the U.S. government. (USCIS lists the types of employment that qualify.) To apply for “preservation” of your permanent residence, you’ll need to submit Form N-470 (officially called the “Application to Preserve Residence for Naturalization Purposes”) to USCIS — in addition to applying for a re-entry permit (see above).

3. Apply for a “returning resident visa.” If you didn’t anticipate needing to stay abroad for one year or longer because of unforeseen circumstances, such as a medical emergency, and therefore did not apply for a re-entry permit before leaving the United States, then it’s essential to apply for a “returning resident visa.” You’ll need to contact your nearest U.S. embassy or consulate (at least three months before you plan to travel back to the United States) and follow their specific instructions for applying. The process usually involves completing Form DS-117 (officially called the “Application to Determine Returning Resident Status”) and an interview with a consular officer, who will determine whether you should receive a returning resident visa based on evidence you provide.

Demonstrating “physical presence”

One of the most important requirements for U.S. citizenship is that you must have physically lived in the United States for at least half of five years (more specifically, 913 days, or roughly 2.5 years) or at least half of three years (more specifically, 548 days, or a little over 1.5 years) if you’re married to a U.S. citizen. Although you’re allowed to take multiple trips outside the United States while you wait out the 3–5 years, it’s important to keep in mind the requirements for “continuous residence” (see above) to make sure you also satisfy the “physical presence” requirement.


When traveling abroad, USCIS will count the days that you physically leave and return to the United States as days that you were physically present in the United States. In other words, if you leave on the January 1 and return on July 1, both of those days would be counted as days that you were “physically present” in the United States.

Those applying for naturalization process based on a certain period or type of military service do not need to meet the “physical presence” requirement. See this eligibility chart to learn how long certain military service members must have physically lived in the United States before applying for naturalization.


This requirement is different from the continuous and physical presence requirements above.

To satisfy the residency requirement, you must have been a resident of the state or USCIS district where you plan to apply for citizenship for at least three months immediately prior to applying for naturalization. (See our detailed guide to naturalization for exceptions to this requirement based on military service.)

“State” also includes the following:

  • The District of Columbia
  • Puerto Rico
  • Guam
  • The U.S. Virgin Islands
  • The Commonwealth of the Northern Mariana Islands

“USCIS district” refers to the geographical area served by a particular USCIS field office, determined by your ZIP code. The “current physical address” you provide on your naturalization application must be where you’ve established residency (that is, where you registered to vote, pax taxes, or obtained a state ID or driver’s license, for example), but there are exceptions. For instance, if you’re a student and depend on your parents or guardians for financial support, you may apply for naturalization from either where you attend school or your family’s home. (For other exceptions, please see the USCIS Policy Manual.)


  • If you move after filing Form N-400 (officially called the “Application for Naturalization”), you must notify USCIS of your new address within 10 days of relocating to your new home so they can forward your naturalization file to the appropriate USCIS field office.
  • USCIS will consider your residency to be the location you specify as your “current physical address” on your Form N-400, even if you decide to apply for naturalization 90 days early.

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Good Moral Character

“Good moral character” is broadly defined by USCIS as character that measures up to the standards of average citizens. Whether an applicant meets this requirement is decided by the government on a case-by-case basis. There are also exceptions for certain military-based applicants (see here for more details). More specifically, having good moral character means that you:

  • Did not commit certain types of crimes — such as murder, illegal gambling, or defrauding the U.S. government for immigration purposes — during the period that begins three or five years before you applied for naturalization and ends when you’ve taken the Oath of Allegiance. (See our guide to the naturalization timeline to learn when in the naturalization process you may need to provide documentation of your interactions with law enforcement.) A USCIS officer may also consider your conduct prior to that period and compare it with your present character — that is, whether your character has improved or not.
  • Did not lie to a USCIS officer during your naturalization interview.
  • Did not receive 2 or more DUI convictions in the three or five years before applying for naturalization and up until the Oath of Allegiance. However, it might not be counted as a negative factor if an applicant is able to demonstrate that they had good moral character during the period in which they committed the offense.


When judging good moral character, USCIS considers an applicant’s original criminal sentence, and rarely takes into account any post-sentencing changes.

English Proficiency and Civics Knowledge

As part of the naturalization process, you will need to pass a two-part naturalization test:

  • An English language test that evaluates your reading, writing, and speaking skills
  • A civics test that evaluates your knowledge of U.S. history and government

The English component combines the naturalization interview with the reading and writing tests. You will be asked about specific answers you provided on your citizenship application, and you will also be asked to write and read simple sentences dictated to you by a USCIS officer.

As for the civics portion, you will need to study either 20 or 100 questions, depending on your age and how long you’ve been a green card holder.

Certain groups of applicants, however, are exempt from one or both tests. Our guide to the U.S. citizenship exam has more details about those exemptions, along with what to expect, how to prepare, and links to study resources.

Filing your application package is only the first step of the naturalization process. It could be several months or more until you obtain U.S. citizenship.

Military and Civil Service Registration

You must be willing to serve in the U.S. military or perform civil service for the United States if you’re ever called upon to do so, which generally means registering with the Selective Service System if you’re a male of a certain age. The Selective Service System is a government program that collects and maintains information on individuals who may be able to serve in the military by draft.

Who is required to register with Selective Service?

Males who have lived in the United States (or received their green card) between the ages of 18 and 26 must register with the Selective Service System. Registration usually must be completed within 30 days after turning 18 but not after turning 26.

Who is not required to register with Selective Service?

Males are not required to register for Selective Service if they:

  • Are over 26 years old
  • Did not live in the United States between the ages of 18 and 26
  • Have lived in the United States between the ages of 18 and 26 but under a lawful status other than “green card holder” during that entire period
  • Were born after March 29, 1957 and before December 31, 1959 (Selective Service was inactive during the time that men born in these years would have turned 18)

How and when can I register with Selective Service if I haven’t already?

If you have not turned 26 and did not already register with Selective Service, it’s important to register before applying for naturalization. Otherwise, your U.S. citizenship application will most likely be denied.

There are multiple ways to register with Selective Service:

  • At your local post office
  • By returning a Selective Service registration card you received in the mail
  • Online

You can check your registration by going online or calling (847) 688-6888. Once you’ve registered, Selective Service will send you a “registration acknowledgement card” by mail to serve as proof of your registration.


USCIS may have already sent your information to Selective Service for registration when you applied for a green card. But sometimes either USCIS or Selective Service doesn’t complete the registration. To check if this is the case — or if you’re simply not sure whether you’ve already registered — you can request a “status information letter” from Selective Service, which would indicate whether you’re registered, as well as whether you were required to register or were exempt from registering.

What if I did not register with Selective Service when I was supposed to?

If you didn’t already register with Selective Service before turning 26, you will no longer be able to register. How you must proceed depends on how old you are at the time you apply for naturalization:


Your only option in this case would be to convince USCIS that you either:

  • Weren’t required to register
  • Were exempt from registering
  • Didn’t know you were supposed to register
  • Registered, but USCIS or Selective Service did not complete the registration process for you

If you weren’t required to register or were exempt from registering, you’ll need to request a “status information letter” from Selective Service, which would indicate either or both of these scenarios, and send a copy to USCIS.

If you didn’t know you were supposed to register, you’ll need to send the following to USCIS (in addition to the status information letter):

  • A notarized personal affidavit (sworn statement) from yourself, explaining in detail that you did not know you were supposed to register (for example, if your high school did not inform you that you would be required to do so upon turning 18 or because you thought only U.S. citizens were required to register)
  • Notarized personal affidavits from other people who knew you and can support your claim

If you intentionally did not register (even though you were required to) — either because you refused or ignored this responsibility — USCIS may deny your citizenship application, but they may also consider your age at the time you apply:

  • If you’re between the ages of 26 and 31, USCIS will likely give you a chance to prove you weren’t required to register or were exempt (see above) before they decide whether to approve or deny your application.
  • If you’ve already turned 31 (or 29, if you’re married to a U.S. citizen), then it may not matter (see below), but your refusal or disregard for this responsibility may be considered a lack of “good moral character” (see above).


USCIS may ignore the fact that you did not register for Selective Service (even though you were required to), and you may not be required to provide documentation (see above).

Again, Selective Service registration is required if you have not turned 26 during the three- or five-year wait period before you applied for naturalization. But if you’re past the age of 26, USCIS will then consider other factors, including how many years you’ve demonstrated “good moral character” (see above).

If you’ve demonstrated good moral character for the required five years (or three years if you’re married to a U.S. citizen) before you apply for naturalization, then USCIS may overlook your lack of Selective Service registration. That’s why some naturalization applicants wait to file their Form N-400 until they’ve turned 31 (or 29, if married to a U.S. citizen), assuming they’ve also waited five (or three) years and satisfied all other naturalization requirements.

Allegiance to the United States

In order to become a U.S. citizen, you must demonstrate an “attachment” to the U.S. Constitution. “Attachment” simply means that you believe, support, and are willing to defend the principles of the U.S. Constitution by accepting the democratic process and promising to obey the law.

How do you demonstrate this “attachment”? You’ll attend a public “swearing-in” ceremony, where you and other naturalization applicants will recite the Oath of Allegiance, the final step of the naturalization process.

During the ceremony, you’ll be asked to make sure that you understand the following:

  • You’re taking the Oath of Allegiance voluntarily.
  • You’re giving your full allegiance to the United States by renouncing your allegiance to all other countries where you claim citizenship.
  • You accept all the responsibilities of a U.S. citizen — including military and civil service if necessary (see above) — and have no intention of not fulfilling these duties.

You must complete this last step before you can become a U.S. citizen.