How to overcome a presumption of abandonment of legal permanent resident status when you study abroad for 9 months?

If you maintain a permanent home address in the U.S. and remain enrolled at a U.S. university, that helps to show you have not abandoned permanent residence. It will be important to note that you failed to file a tax return only because you had insufficient income and thus did not owe any tax. However, you cannot file the N-400 while you are in school abroad: you must be back in the U.S. and living full-time in the state where you will file the N-400 for at least 3 months before you are eligible to file. You also need to carefully tally the dates of all your time outside the U.S., both because you must list all your actual dates outside the U.S. since becoming an LPR on the N-400 form, and because you need to make sure that you wait to file until you meet the cumulative physical presence requirements. In order to be eligible to apply for naturalization, you must have been physically present in the United States for at least 30 months, or at least half of the 5 year period prior to your application.