A taxpayer can use a tax or W-4 calculator to estimate his tax refund or liability, according to H&R Block. A tax calculator typically uses the taxpayer's filing status, number of dependents, income and expenses to determine taxable income and credits.
Income entered on a tax calculator includes interest income, divided income, capital gains/loss, Social Security benefits and non-taxable combat pay, notes H&R Block. Examples of qualifying expenses include charitable donations, state taxes, child care expenses, interest from student loans and tax preparation fees.
In addition to determining tax refunds, W-4 calculators can help determine whether an employee is having too much or too little federal income tax withheld from his check, according to H&R Block. W-4 calculators require pay frequency, paycheck gross, final check date, current allowances and payroll deductions to determine a tax refund or how much the individual owes the IRS.
If a taxpayer's employer failed to withhold enough federal income tax to keep the employee from owing the IRS, the employee should consider filling out a corrected W-2, notes The Nest. The form can be used to correct or amend a tax return. Both the employee and the employer are required to file a corrected W-2 form to the Social Security Administration.