Which of the following is considered a mandatory payroll deduction?

Federal income tax withholding is classified as a mandatory payroll deduction because it is required by law for employers to withhold a certain amount of tax from employees' wages. This withholding serves to ensure that employees contribute their fair share toward federal income taxes throughout the year, ultimately reducing the burden when they file their annual tax returns. Since businesses are legally obligated to engage in this withholding process, it is considered a mandatory deduction.

In contrast, other options like health insurance premiums, charitable contributions, and retirement savings contributions are typically considered voluntary deductions. Employees can choose whether to participate in these programs, making them non-mandatory payroll deductions. Therefore, while they may affect an employee's net pay, they do not carry the same legal requirement as federal income tax withholding.