Dual-status aliens are resident aliens and nonresident aliens at different times in the same tax year. This most commonly occurs in the year a person arrives in the U.S. or leaves the U.S. It may also occur if residency status changes during the year.
Completing dual-status returns is an advanced task and not covered by the volunteer program. Refer dual-status taxpayers to your site coordinator and/or a paid preparer. More information is in IRS Publication 519, U.S. Tax Guide for Aliens.