Instructions for IRS form 1040 can be found online on the IRS website. The website has instructions for both the current as of 2015 forms, as well as forms from previous tax years.
IRS Form 1040 is one of three different forms people in the United States can use to pay their federal taxes. It is the most complex of the three forms, allowing users to input the maximum number of income sources and deductions.
There are a number of reasons why a taxpayer might be required to use Form 1040. For example, those who own their own businesses, received income from self-employment, earned money overseas or are claiming an adoption or first-time home buyer credit cannot file using simplified forms.