In most situations, a person who is physically present in the United States for at least 183 days out of any calendar year is a US resident for tax purposes and must file Form 1040 as a tax resident. There are exceptions to this general rule, but none of them apply to people who are present in the United States in H-1B (guest worker) status. Furthermore, H-1B workers are categorically resident aliens for tax purposes and must pay taxes on the income they earn while in H-1B status as a resident alien in every year in which they earn more than the personal exemption limit. This includes both the first year and last year, even if the first or last year contains less than 183 days of residence in the United States. The short years may result in a filing as a u201cdual-statusu201d alien.An H-1B worker will therefore only file Form 1040NR as his or her primary tax return in the tax year in which he or she leaves the United States permanently, and all US-connected income during that year will be taxed as if the taxpayer was a US resident, under the dual-status rules. All other tax returns during that personu2019s residence in the United States will be on Form 1040. The first yearu2019s return may be under dual-status rules, with a Form 1040NR attached as a u201cdual status statementu201d as per the procedure in Chapter 6 of Publication 519 (2023), U.S. Tax Guide for Aliens. A person who resides the entire year in the United States in H-1B status may not use Form 1040NR, and is required to pay US income tax on his or her worldwide income, excepting only that income which is subject to protection under a tax treaty.See Publication 519 (2023), U.S. Tax Guide for Aliens for more information. The use of a tax professional, especially in the first and last year of H-1B status, is highly recommended as completing a dual-status return correctly is exceedingly challenging.