A form one files with the
IRS to claim that one is not subject to
withholding tax under the foreign earned income exclusion. In general, an American
employer must withhold from U.S. citizens working outside the United States, but the employee may claim an exemption to this if he/she does not believe his/her
income earned overseas will exceed the threshold for U.S. taxation, as one generally does not pay taxes on foreign income below a certain level. Form 673 is one way to make this declaration, though there are other forms with which to do so.