Form 8840, also known as Closer Connection Exception for Aliens Statement, must be filed with IRS before the due date for filing of US income tax return for individuals. The due date for filing the income tax return in the US is the 15th of April whereas for the individuals who do not have US source employment income due date is the 15th of June. This form is filed even if you do not have US income. As mentioned before US taxes worldwide income of US residents so skipping this form may have serious tax consequences.