Which of the following is used by employers to determine how much income tax to withhold from employee wages?

The correct choice is allowances claimed. Employers use the number of allowances an employee claims on their W-4 form to determine the amount of income tax to withhold from their wages. Each allowance reduces the amount of income subject to withholding tax. The more allowances an employee claims, the less tax will be withheld from their paycheck, as it indicates that the employee expects to qualify for more deductions or credits when they file their tax return.

Other factors, such as tax brackets, yearly income, and filing status, do influence tax calculations overall, but they are not the direct basis used in the withholding calculation process. The tax bracket establishes the rate at which income is taxed, yearly income determines total tax liability, and filing status affects overall tax rates and deductions, but the specific mechanism for withholding is primarily tied to the allowances claimed.