Middle Class Tax Break Act of 2017 This bill amends the Internal Revenue Code to allow a working America tax credit equal to the lesser of: (1) 6.2% of the earned income of the taxpayer, or (2) $500 ($1,000 in the case of a joint return or a head of a household). Individuals whose modified adjusted gross income does not exceed $100,000 ($200,000 in the case of a joint return or a head of a household) are eligible for the credit. The following individuals or entities are ineligible for the credit: (1) estates or trusts, (2) nonresident aliens, (3) individuals who do not include a Social Security number on their tax return, and (4) individuals for whom another taxpayer is allowed a deduction for a personal exemption.