Employed individuals who wish to determine if they are having too little or too much federal income tax withheld from their paychecks can find a free online withholding tax calculator at the IRS website. Under the column heading "Hot Topics" on the IRS home page, the link "Time to Adjust Your Tax Withholding?" takes site visitors to the instruction page for using the online calculator. About halfway down the instruction page, the link "Continue to the Withholding Calculator" opens the calculator input page.
Searching the Internet will bring up various types of free tax calculators, but disclaimers will also be found, such as the CalcXML tax calculator at the Erie Federal Credit Union website, which advises users that the results obtained "should not be construed as legal, financial or tax advice." The IRS website advises its withholding tax calculator users that individuals subject to other forms of taxation, such as self-employment tax or alternative minimum tax, will be better served by consulting IRS tax document Pub 505, Tax Withholding and Estimated Tax.