Yo bud, the bottomline b that In order to claim individual, in this case ur mother, as ur dependent, she has to be a U.S. resident for income tax purposes. during ur tax years in order to claim her as dependent.
However,the designation of resident for tax purposes is completely separate from ur mother's immigration status. Ur mother might qualify as a resident for tax purposes while remaining a nonimmigrant alien for immigration purposes. And then u calaim ur mother as ur dependent for dependency tax exemption, then ther will b no problem at all. To b a resident for tax purposes, ur mpther needs to pass the residency test..
"혹 이게 시민권이 통과되는 데에 문제가 될 수 있는지요....걱정입니다"---Requirements to become a naturalized US Citizen doesn't require ur tax returns Immigration wants an applicant's IRS tax return “transcript” or an IRS-certified tax return listing tax information for the last five years (or for the last three years
to see how the applicant earns his.her financial income to finacially support himself/herself. But immigration can deny citizenship application for "failure to file U.S. tax returns" meaning u do not file your return by the due date including extensions or etc.
". .나중에 엄마 영주권이 진행되는 데에 걸림돌 이 되지는 않을런지요..."---Unfortunately, ur mother cannot simply apply for Green Card based on her several year residency in the United States. However, if she gets apprehended by the Immigration and Customs Enforcement, she could file for Cancellation of Removal before the Immigration Judge. If the judge grants Cancellation of Removal, she will get a Green Card. For some inexplicable reason, she cannot apply for Cancellation until she b actually placed in Removal Proceedings.
Hope this helps~~~~