Employees who would like to change their withholding to reduce their tax refund or their balance due;

Employees whose situations are only approximated by the worksheets on the paper W-4 (e.g., anyone with concurrent jobs, or couples in which both are employed; those entitled to file as Head of Household; and those with several children eligible for the Child Tax Credit);

Employees with non-wage income in excess of their adjustments and deductions, who would prefer to have tax on that income withheld from their paychecks rather than make periodic separate payments through the estimated tax procedures.