My son will be 18 in March 2010 and we all have in “Green Card” for almost five years (less than two months). What is our choice? Can we start to fill in N400 now (it said N400 can be filed in advance – three months). How to fill in the form and actually this is in advance? What is our son’s choice? He can file now or he has to wait until he is 18? Thanks for your comments.