Massachusetts Schedule A is a form used to calculate and report the Massachusetts state income tax owed. It is part of the Massachusetts state income tax return (Form 1). There are two types of Massachusetts Schedule A: Form 1-NR/BY for nonresidents and part-year residents, and Form 1 for full-year residents. The form is used to calculate the tax due based on income, deductions, and credits related to Massachusetts income. It is important to complete Schedule A accurately as it determines the tax owed to the state of Massachusetts.