Which of the following is a common payroll tax that employees must pay?

The Social Security tax is a common payroll tax that employees must pay as it is specifically designed to fund the Social Security program, which provides benefits for retirees, the disabled, and survivors of deceased workers. This tax is deducted directly from employees' wages and is a significant component of the broader payroll tax system in the United States.

The amount deducted is typically a percentage of the employee's earnings, up to a certain income limit, ensuring that contributions to the system correlate with income levels. Employers also contribute an equal amount to the Social Security tax, which reflects the shared responsibility of funding the program.

In contrast, capital gains tax, property tax, and sales tax do not function as payroll taxes. Capital gains tax applies to the profit made from the sale of assets, property tax is a levy on real estate based on its value, and sales tax is charged on the sale of goods and services rather than on wages or salaries. Thus, Social Security tax is the only option that specifically relates to payroll deductions made from employee earnings.