IRS Form 1040 is the standard individual income tax return form for United States taxpayers. While this is one of the most common forms taxpayers encounter, it can be complicated to manage. Form 1040 tends to undergo many changes each year as the complex tax code faces new legislation. It is important to stay on top of these alterations as they can impact the amount of income taxes owed to or refunds received from the IRS. Form 1040 has to be filed by most citizens of the U.S. The IRS recommends filing the form even if it is not required.