Unfortunately, a common problem I see with my clients is the misunderstanding of what all is required for one to become naturalized. The most common issue that people have problems with and do not understand properly are the concepts of continuous residence and physical presence.
Continuous Residence basically means that the applicant has maintained residence in the United States for a specified period of time. Normally, you must have 5 years of continuous residence to apply for naturalization. However, if you are married to a US, the requirement for continuous residence is reduced to 3 years while married to the US citizen spouse.
Physical Presence means that the applicant was physically present in the United States for a specified period of time over the course of 5 years. Generally, a person must be physically present in the United States for 30 months out of the 5 years to be eligible to naturalize. For a person who is married to a US Citizen spouse, the requirement for physical presence is 18 months, meaning that out of the 3 years of continuous residence, the permanent resident spouse must be physically present in the US for 18 month.
The problem and misunderstanding that many people have is that once they have a green card, they can come and go from the US as they like without any repercussions. They have a mistaken idea that no matter how long they travel abroad, the time that they accumulate in the US can all be used to towards their continuous residence and physical presence requirements for naturalization. This idea or thought process is greatly flawed and results in a big surprise when the client visits my office and learns that they are not eligible to apply for naturalization.
When in doubt, speak to a knowledgeable immigration attorney to understand your eligibility for naturalization.