What document is used by an employee to determine how much tax should be withheld from their paycheck?

The document used by an employee to determine how much tax should be withheld from their paycheck is the W4 form. When starting a new job or when there are changes in personal circumstances (such as marriage or having a child), employees fill out the W4 to provide their employer with information about their tax situation. This form includes details such as the employee's filing status and the number of allowances they are claiming, which directly impacts the amount of federal income tax withheld from their earnings. By accurately completing the W4, employees can ensure that the correct amount of tax is withheld, helping them avoid underpayment or overpayment of taxes throughout the year.

In contrast, the W2 form summarizes an employee's annual earnings and the total amount of taxes withheld, but it does not determine withholding amounts. The 1099 forms are used for various types of income that are not wages, such as interest or freelance income, and they serve different reporting purposes, not for withholding tax directly from a paycheck.