Individual Taxpayer Identification Numbers
IRS regulations require that each person listed on a U.S. federal income tax return have a valid Taxpayer Identification Number (TIN). The types of TINs are:
Social Security Numbers
One of the first things you should do when preparing an individual's tax return is to ask for a social security card for each individual who will be listed on the return. Then, verify the accuracy of the social security number and the spelling of the individual's name by ensuring that the information on the tax return matches the social security card.
Taxpayers who cannot substantiate their identity should seek a professional tax preparer.
Canadians have a number that is like a social security number, but it's for their old age pension. Do not use this number on a U.S. tax return. Canadians often have both a U.S. and Canadian social security number.