请问：绿卡居住美国时间已过5年，但从来没有报过税，可以申请入籍吗？
-Why did you not file tax return? You should have file it every year even if you did not have income. This is required by law. See:
http://www.uscis.gov/green-card/after-green-card-granted/rights-and-responsibilities-permanent-resident/rights-and-responsibilities-green-card-holder-permanent-resident
So, unless you have the evidence to justify why you did not file tax return since you became a green card holder such as all the correspondences with the IRS concerning your failure to file, you had better not apply for the US citizenship.
