Missouri Form 15 is a state tax form used by Missouri residents to file their income tax returns. There are two different types of Missouri Form 15: the Missouri Individual Income Tax Return and the Missouri Nonresident and Part-Year Resident Income Tax Return. The Missouri Individual Income Tax Return is used by full-time and part-time Missouri residents to file their income taxes. This form is used to report all income, adjust income, calculate tax liability, and claim credits and deductions. The Missouri Nonresident and Part-Year Resident Income Tax Return is used by individuals who lived in Missouri for part of the year or are nonresidents of Missouri. This form is used to report income earned from Missouri sources and calculate the resulting tax liability.