nepwanted, You did not mention what status they are holding now. It is very important. If they are US Citizen it don't matter they don't need to inform any authorities, but if they are GC holder then it depends whether they want to maintain their residency and protect their status with GC.

yeah they have GC and its been just a year they are here. Its obvious that everybody wants to maintain his/her status. Thats why i am asking where should we go to inform. thanks

Hey nepwanted, i heard for GC holder wanting to stay outisde of continental US for more than a year can pay some sort of $100 fee?fine? per year and live outside upto the life of GC. i haven't verified it but heard it from a creditable source, so you might want to check out uscis.gov or may be even send them an email. if nothing works, just have your folks make a new nepali passport before they re-enter US, as the new passport won't have any departure date and immigration doesn't keep track of when you left the country other than from what is stamped on your passport. plus they don't really profile elders that much anyways so i wouldn't be too worried...my folks haven't had any issues staying pass a year on many occasion.

A Green Card or Permanent Resident Card is an individual’s proof of lawful permanent resident status in the United States. An individual with a Green Card has the right to live and work permanently in the United States. Green Card holders have to follow immigration law and be properly registered with the United States government. Green Card holders are entitled to depart the United States on vacation or for work purposes. However, there are limitations on how long an immigrant can stay outside the United States without losing his or her permanent resident status (Green Card). A document called a "Reentry Permit" must be obtained from the USCIS in many cases. Note: Only Green Card holders may obtain a reentry permit when visiting foreign countries. United States citizens and foreign nationals on nonimmigrant visas don't need to obtain a "Reentry Permit". The purpose of applying for and obtaining a reentry permit is to preserve an alien's permanent resident status (Green Card). Green Card holders leaving the United States for a long period of time and without obtaining a reentry permit may risk losing their Green Cards. There are different requirements that all permanent residents should be aware of when traveling abroad with a Green Card. Individuals leaving the United States for over a certain amount of time are required to apply for and obtain a reentry permit. However, an individual may depart the U.S. as long as the application is submitted in the United States. The problem with applying in advance and leaving the country before the permit is approved is that the application may be denied, hence creating a problem upon returning to the country. It may be possible to obtain a returning resident visa, but this is not guaranteed.

NEPWANTED Hey man, why you wanna back, go www.uscis.gov and fill the I-131 form and pay $ 305 and you will get reenter permit and you can live nepal up to 2 yrs... But re-enter permit takes time 4-5 month .

thanks everybody for your valued sugestions. I really appreciate it.